Brake fluid is a hydraulic fluid that is used in hydraulic clutch applications and hydraulic brakes in automobiles. Apart from transferring force into pressure, brake fluid also amplifies braking force. It achieves all these because it is not substantially compressible.
The braking systems of modern heavy commercial vehicles, high speed cars extra, are subject to increasingly high temperatures. Any brake fluid you use must; therefore, possess adequate thermal stability and low vapor pressure.
In addition, the best brake fluid must display suitable flow properties over the entire range of anticipated operational temperatures. It should lubricate and protect all metal components against corrosion, and be fully compatible with elastomers and seals.
The choice of brake fluids is huge in today’s market, and not everyone can make the best buying decision. I understand you better, and that is why I have come up with this resourceful and informative guide to help you with your selection.
Brake Fluid Comparison Chart: Quick Look
|Product Name||Type||Dry Boiling Point (°F)||Wet Boiling Point (°F)||Quantity (ml)||Price|
|MAG1 120 Premium||DOT 3||492||284||946||Check Price|
|Castrol SRF 12512||DOT 3||590||518||1000||Check Price|
|Endless RF650||DOT 4||622||424||500||Check Price|
|Motul MTL100949 8068HL||DOT 4||594||399||500||Check Price|
|ATE 706202 Original TYP 200||DOT 4||536||388||1000||Check Price|
|Maxima 80-81911||DOT 5||500||356||325||Check Price|
|Johnsen’s 7012-6||DOT 5||No Data Available||No Data Available||355||Check Price|
|Motul (N-S)||DOT 5.1||500||356||500||Check Price|
|Wagner Severeduty||DOT 5.1||No Data Available||No Data Available||946||Check Price|
|Ravenol J3A1001||DOT 5.1||536||356||1000||Check Price|
Top 10 Brake Fluid Reviews
Here’s the need-to-know stuff. We researched and make a list of top brake fluids available on the market now and also defined as DOT categorized. So that, you’ll know which is the best for your vehicle without giving a second thought.
MAG1 120 Premium – Best DOT 3 Brake Fluid
As far as DOT 3 fluids are concerned, the MAG1 is the best overall. It is the ideal choice for vehicle maintenance as well as performance. It uses FMX technology that offers supreme performance and protection.
This fluid features a specially combined formula that exceeds or meets the highest safety and performance standard for DOT 3 fluid. It is the ideal choice for all drum and disc brake systems, together with ABS.
Unlike conventional products, this model meets the minimum requirements of FMVSS 116, and it exceeds SAE specs. It has a minimum dry boiling point of 492°F and a minimum wet boiling point of 284°F.
With MAG1, you should expect evolutionary performance. Even though it is a DOT 3 grade, this fluid is capable of meeting the tough challenges of efficiently balancing durability, strength, and performance.
Things We Liked:
- Complies with FMVSS 116
- Reliable boiling points
- Compatible with many car brands
- Compatible with other brand fluids
- A great flushing fluid
Things We Didn’t Like:
- Doesn’t offer the superior performance of DOT 4
- Part number: 120
- Package Weight: 1.061 kilograms
- Package Dimensions: 8.991 L x 22.402 H x 8.991 W (centimeters)
- Included components: MAG1 120 Premium DOT 3 Brake Fluid - 32 oz.
Castrol SRF – Best DOT 3 Racing Brake Fluid
If you are looking for the ultimate brake fluid for racing in wet conditions, look no further than the Castrol React SRF. Unlike other brake fluids in its category, the Castrol React SRF exceeds the FMVSS 116 DOT 3 and DOT 4, JIS K2233, ISO 4925, and SAE 1703.
This fluid features distinctive silicon ester technology that does a great job of absorbing less water than regular glycol ether brake fluids. It also prevents performance deterioration during high temperatures.
Even though this fluid is graded as DOT 3, it has outstandingly high boiling points: dry (590°F) and wet (518°F). These high boiling points are capable of withstanding extreme temperatures. It is the premier choice for racing and motorsport hydraulic brakes.
The Castrol SRF comes with supreme anti-vapor qualities. This fluid is safe to use with all non-mineral oil based disc as well as drum brake systems. However, you are advised by the manufacturer not to mix Castrol SRF with mineral based fluids or DOT 5 silicon fluid.
Things We Liked:
- Exceeds FMVSS 116 DOT 3 & DOT4, JIS K2233, ISO 4925, and SAE 1703
- Offers superior anti-vapor lock qualities
- Outstandingly high boiling points
- Safe for disc and drum brakes that are non-mineral and oil based
- Its silicon ester technology is compatible with DOT 4 brake systems
Things We Didn’t Like:
- A bit expensive compared to other DOT 3 models
- An exclusive European formula with an exceptionally high boiling point and superior anti-vapor lock characteristics
- Superior braking during arduous conditions like racing and rallying
- Typical wet boiling point is 270deg. C
Endless RF650 – Best DOT 4 Racing Brake Fluid
This amazing product is used in Dakar Rally, WRC, and Formula 1, but it is also an accessible choice for drivers who desire high performing brake fluid. It allows for stable performance characteristics to be achieved during very high heat situations.
It has even viscosity and high velocity, which allows for precise and fast braking irrespective of the temperature. It is designed to withstand low freezing point of -40°C, making it ideal for snow rallies.
It has an extremely high dry boiling point of 622°F, which proves how effective this fluid can be during extreme hotness. It does also have an outstandingly high wet boiling point of 424°F, which makes it the ideal choice for humid environments because it absorbs minimal humidity.
Things We Liked:
- It exceeds DOT specifications
- Super high dry boiling point for supreme braking performance
- Outstanding wet boiling point for superior braking in humid conditions
- Capable of achieving remarkably stable performance characteristics
- Offers precise and fast braking irrespective of high temperatures
Things We Didn’t Like:
- Slightly expensive compared to similar products of the same quantity
- Used in Formula 1, WRC and Dakar Rally
- Ability to maintain dry boiling point
- Much stiffer and consistent brake pedal with its superior compressibility characteristics
- Becoming recognized as the highest-spec brake fluid around the world
- Even though RF-650 is marketed as a race brake fluid it can be used in all types of vehicles
Motul MTL100949 8068HL RBF 600 – Best DOT 4 Synthetic Racing Brake Fluid
The Motul RBF 600 is poly-glycol based, and it is 100% synthetic fluid. It is the best choice for the hydraulic actuated brake as well as clutch systems that require a non-silicone synthetic fluid. It is specially made to withstand high temperatures.
It has an extremely high dry boiling point of 594°F, which is superior to regular DOT 5.1 and DOT 5 brake fluids. This is, in fact, one of the highest performing DOT 4 brake fluids I have used. It allows for effective braking even under punishing conditions.
It is an efficient choice for when rainy. It has a remarkably wet boiling point of 399°F, which is also superior to regular DOT 5.1 brake fluids. Unlike conventional DOT 4 and 5.1, the Motul RBF 600 does not absorb too much humidity.
Apart from racing applications, you can use this fluid for everyday driving. However, it may be overkill for some conventional car models, since it is meant for high heat applications. It is indeed an excellent choice for the money.
Things We Liked:
- The very high boiling point that exceeds conventional DOT 5 and 5.1
- Superior thermal resistance as well as stability
- Non-silicone synthetic fluid for hydraulic actuated brake & clutch systems
- Offers unmatched aerodynamic performance
Things We Didn’t Like:
- No shelf date is available for this product.
- For hydraulic actuated brake and clutch systems
- Non-silicone synthetic fluid
- Extreme thermal resistance and stability
- Very high boiling point (312 degree centigrade / 594 degree Fahrenheit)
- Better aerodynamic performance
ATE 706202 Original TYP 200 DOT 4 – Best Brake Fluid For BMW
This is a high performance DOT 4 brake fluid. It is a safe and effective choice for the racing experience. It does a good job of handling the extreme demands of motor racing. It offers great value for money.
It has an outstanding dry boiling point of 536°F, which exceeds the minimum point of convectional DOT 5.1/5. It also has an outstandingly high wet boiling point of 388°F, which means the fluid absorbs minimum moisture and has the highest safety reserves.
This DOT 4 motor vehicle brake fluid meets as well as surpasses the requirements of FMVSS 116, Class 4, ISO 4925, SAE J1704, and SAE J1703. It has superior safety tolerance against steam bubbles, and it is non-foaming when bleeding or filling the brake system.
The manufacturer advises you to be careful with this fluid since it is capable of dissolving paint. You should avoid misuse. Make sure you follow the manufacturer’s guidelines when filling or changing the brake fluid. Also, avoid mixing this product with synthetic fluids, such as DOT 5.
Things We Liked:
- Has high dry and wet boiling points
- Superior safety tolerance against steam bubbles
- Selected additives ensure exceptional corrosion protection
- It is non-foaming when bleeding and filling
- Superior water locking properties ensure minimal boiling point decrease
Things We Didn’t Like:
- There is no possibility of changing color.
- Minimal decrease of boiling point due to excellent water locking properties
- Non-foaming when filling and bleeding the brake system
- Excellent corrosion protection due to selected additives
- High safety tolerance against steam bubbles
- Makes brake fluid changing intervals of up to 3 years possible
Maxima 80-81911 – best dot 5 silicone brake fluid
The Maxima 80-81911 brake fluid is a silicone based fluid with very high boiling temperatures. It has a dry boiling point of 500°F, which exceeds most convectional DOT 4, 5, and 5.1 in the market. And has a wet boiling point of 356°F, which is ideal for humid conditions.
Maxima 80-81911 brake fluid offers superb lubrication to metals and rubber seals and does a fantastic job of preventing corrosion since it does not absorb water. It will hardly affect paint, and it is effective at extending the brake system life cycle.
Its advanced silicone supreme formula features the latest additives that help to ensure that the hydraulic brake & clutch systems work properly, and prevent vapor lock. This DOT 5 brake fluid can be mixed with other DOT 5.
Things We Liked:
- Has high dry and wet boiling points for superior performance
- Silicone supreme formula features the latest additives
- Anti-vapor lock formula prevents vapor lock
- Compatible with other DOT 5 products
Things We Didn’t Like:
- Available in small capacity bottle
Johnsen’s 7012-6 Silicone DOT 5 Brake Fluid – best for harley davidson
Johnsen’s 7012-6 is a silicone based braking fluid. It offers 450 degrees protection for both drum and disc brakes. Unlike most conventional products, Johnsen’s 7012-6 guarantees optimal performance of the brake system.
It meets/exceeds the requirements of FMVSS 116 and does not absorb water. This DOT 5 fluid will do a remarkable job of extending the service life of your brake system, and will hardly affect paint. It is the ideal choice for racing motorcycles and vehicles.
Things We Liked:
- Meets/exceeds the FMVSS 116
- Will not absorb water, so it maintains superior operation
- No paint damage when it spills
- Lasts for a long time before change is required
Things We Didn’t Like:
- Not suitable for silicone or mineral oil systems
- Specially formulated hydraulic brake fluid that provides superior benefits
- Johnsen's Silicone DOT 5 Brake Fluid is essentially non-hydroscopic compared to conventional DOT 3 or DOT 4 brake fluids, absorbing less than one percent by weight of water
- For drum and disc brakes
- Not to be used in ABS systems
- 500°F Protection
Motul DOT 5.1 (N-S) – hydraulic brake fluid
This is a poly-glycol based brake fluid that is 100% synthetic. It is the perfect choice for hydraulic actuated brakes as well as clutch systems. This is in accordance with DOT 3, DOT 4, and DOT 5.1 manufacturers’ recommendations.
This modern generation brake fluid offers additional user safety, and it easily exceeds the requirements of DOT 4 and DOT 3. Its low viscosity formulation makes it the perfect choice for use in cold conditions and for automobiles with ESP / ABS systems.
It has a high minimum dry boiling point of 500°F, which allows for supreme braking under vigorous conditions. It also features a minimum wet boiling point of 356°F, making it ideal for humid conditions.
Things We Liked:
- Conforms to and exceeds FMVSS 116
- Compatible with DOT 4 and DOT 3 brake fluids
- Provides additional user safety
- Suitable for cold climates and vehicles with ESP / ABS systems
Things We Didn’t Like:
- Not suitable for silicone or mineral oil systems
- In accordance with DOT 5. 1, DOT 4 and DOT 3 manufacturers recommendations
- Brake fluid
- 100% synthetic
Wagner DOT 5.1 Severeduty Brake Fluid
The Wagner Severeduty brake fluid is designed as well as tested to meet or surpass original equipment specs. It is a non-silicone brake fluid, so it is completely mixable with other non-silicones, such as DOT 4 and DOT 3 fluids.
This product adds corrosion and rust inhibitors to your brake system to maximize the life cycle. It also features special additives that optimize performance at very high temperatures. This is a perfect choice for light trucks and passenger cars.
Things We Liked:
- Helps to provide a quieter brake system
- Delivers smoother pedal travel
- Guarantees proper movement for effective braking
- Delivers longer brake life as well as performance
Things We Didn’t Like:
- Not the ideal choice for mineral oil/silicone systems
- Maintains proper movement for safe, effective stopping performance
- Helps deliver a quieter braking system
- Produces smoother pedal travel
- Provides longer brake life and performance
- Install Wagner with total confidence
Ravenol J3A1001 DOT 5.1 SAE J1703 – Best Synthetic Brake Fluid
If you are looking for the best DOT 5.1 fluid for vehicles with ABS characteristics, look no further than the Ravenol DOT 5.1. It has superior chemical stability, and it features additives that provide the most excellent lubrication efficiency.
Its unique formulation ensures that it exceeds the minimum requirements of FMVSS 116 DOT 5.1, ISO 4925, and SAE J1704. This unique product can be used in all automobiles with DOT 5.1 specifications.
It is gold in color and has a minimum dry boiling point of 536°F, which is ideal for maintaining supreme brake performance under extreme conditions. It also has a minimum wet boiling point of 356°F, which is ideal for humid conditions.
Things We Liked:
- Meets/exceeds FMVSS 116 DOT 5.1 and international specifications
- Offers superior efficiency and lubrication for ABS and brake systems
- Remarkably high minimum dry and wet boiling points
- Applicable for clutch systems and hydraulic braking
- Compatible with non-silicone brake fluids
Things We Didn’t Like:
- Not compatible with mineral oil and silicone based systems
- Please see Product Description regarding the California Proposition 65 Warning
- Great ABS and brake systems efficiency and lubrication, designed for excellent resistance to moisture absorption
- Gold in color with a dry boiling point of 536° F and a wet boiling point of 356° F
- Long life brake fluid formulation designed for extreme frequent braking; Applicable for hydraulic braking and clutch systems
- Compatible with all brake systems requiring DOT 5.1 brake fluids
Factors to Consider When Buying Brake Fluid
Types of Brake Fluid
Brake fluid is the indispensable factor of an automobile braking system. Basically, the force you exert on the brake pedal may not be transferred effectually to the brake disc, pads, and caliper if the fluid used is not enough.
Usually, there is confusion regarding the types of brake fluid as well as their capability of existing or performing in harmony. The American DOT system evaluates brake fluids, and that is how they are named (DOT 3, DOT 4, DOT 5, and DOT 5.1).
All the types of brake fluids found in the market are poly-glycol ether based. However, there is one major exemption, DOT 5 (silicon based). The major difference among the various brake fluid types is their boiling temperature, viscosity limit, and chemical composition.
|Brake Fluid Grade||Chemical Composition||Dry Boiling Point (°F) @ 0.0% H2O||Wet Boiling Point (°F) @ 3.7% H2O||Viscosity Limit (mm2/s) CP @ -40°F|
|DOT 5.1||Borate Ester / Glycol Ether||500||356||900|
|DOT 5||Silicone Based||500||356||900|
|DOT 4||Borate Ester / Glycol Ether||446||311||1800|
|DOT 3||Glycol Ether Based||401||284||1500|
|DOT 2||Castor Oil / Alcohol||374||284||Data Not Available|
DOT 2 brake fluid is mainly oil based, and it is not a commercially available fluid. This particular fluid has the lowest dry and wet boiling points. Therefore, if your car is required to use DOT 5, 4, or 3, then under no circumstances should you use DOT 2 fluid.
DOT 3 brake fluid is the bargain basement stuff you find in discount auto part stores. This is a rudimentary brake fluid with a moderate water content, which is not popular with contemporary vehicles.
DOT 4 is a high performance brake fluid than DOT 3. You can view DOT 4 as an upgrade of DOT 3 with lower water content. Most modern automobiles use DOT 4, since it is a good compromise between performance and cost.
However, DOT 4 brake fluid is more susceptible than DOT 3. You are likely to find your DOT 4 degraded to DOT 3, if you leave a bottle of DOT 4 brake fluid open for more than two weeks.
DOT 5 brake fluid is a silicon based fluid that does not absorb water and does not attack the paint. This specific type of fluid should not be mixed with other types of brake fluid.
It is heavier in viscosity, which can sometimes cause tiny bubbles of air to become trapped during the bleeding process, resulting in a spongy feeling in the brake pedal. The higher oil viscosity can also affect the performance of the antilock braking system in some cars.
Lack of confidence in silicone based brake fluids led to the introduction of DOT 5.1 brake fluid. Unlike its counterparts, DOT 5.1 fluid offers the performance benefits of silicone, and at the same time retaining some compatibility and familiarity with poly-glycol fluids.
Why is Brake Fluid Hygroscopic?
Poly-glycol fluids are hygroscopic, meaning that they readily absorb water from moisture from the air at normal atmospheric pressure. The water vapor absorbed will eventually get into the brake fluid system via microscopic holes in joints, seals, and brake hoses.
Characteristics of Brake Fluids
The best brake fluid has specific characteristics that are in accordance with certain quality standards.
The Department of Transportation standard sets a wet boiling point and dry boiling point when the brake fluid has absorbed just about 3.5% of water. I have prepared the following comparison table to help you understand the various dry and wet boiling points of brake fluids.
Dry vs. Wet Boiling Point
The most apparent differences among the various brake fluid grades are the minimum boiling points as listed in the table below.
|Brake Fluid||Dry Boiling Point (°F)||Wet Boiling Point (°F)|
The boiling point is important because the heat generated by braking can enter the hydraulic system. If the temperature rises too high, the fluid can boil and form the vapor in the brake lines. This will ultimately reduce the braking power of the system.
The dry boiling point is the minimum boiling point of the new, uncontaminated fluid. After a brake fluid has been in service for some time, the boiling point drops because of water contamination.
On the other hand, the wet boiling point is the minimum boiling point of a brake fluid after it has been exposed to the atmosphere long enough to absorb a given amount of moisture content.
Your brake system operation will only be reliable if the brake fluid retains a constant viscosity over a wide range of operating temperatures. Constant viscosity is important for stability control, traction control, and an anti-lock braking system.
Therefore, the viscosity suggested by the manufacturer is important to consider. Usually, DOT 5.1 brake fluids are considered to have low viscosity over an extended temperature range. However, not all cars equipped with ESP or ABS specify DOT 5.1.
|Brake Fluid Grade||DOT 3||DOT 4||DOT 5||DOT 5.1|
|Viscosity Limit (mm2/s) CP @ -40°F||1500||1800||900||900|
I find corrosion to be one of the most important considerations. You do not want to buy a brake fluid that will corrode the metallic parts of your car, such as ABS control valves, master cylinders, wheel cylinders, and calipers.
The best brake fluid must protect against corrosion since water vapor usually enters the brake system. To achieve the required level of corrosion resistance, manufacturers add additives (corrosion inhibitors) to their products.
Silicone is normally less corrosive and safe for your vehicle’s paintwork. However, glycol ether based brake fluids are corrosive to some level. I strongly advise you to immediately wipe off any spillage when topping the reservoirs of your vehicle.
The finest brake fluid is expected to sustain a low level of compressibility. The low level of compressibility should be able to accommodate different environmental conditions with varying temperatures. This allows for a consistent brake pedal feeling.
Brake Fluid Compatibility
Although, the performance requirements of DOT 5.1, DOT 4, and DOT 3 brake fluids are different, FMVSS 116 needs that the three grades of brake fluid to be compatible with each other in a system.
Mixing different types of brake fluids in a brake system is not recommended, but it can be done without creating a damaging reaction or damaging the system between two types of brake fluids.
It is important to remember that if DOT 4 and DOT 3 brake fluids are mixed in a system, the boiling point of the DOT 4 brake fluid will be reduced by the same percentage as the percentage of DOT 3 brake fluid in the mixture. This may compromise the overall performance.
Even though FMVSS 116 requires DOT fluids to be compatible, it does not need them to be identical. They are not required to blend into a single solution, unless the brake fluids are of the same type, such as two DOT 4 brake fluids.
You should remember that silicone DOT 5 brake fluid has lower specific gravity than poly-glycol brake fluid. If you mix the two types, they will not blend. The silicone fluid will separate and float on top of the poly-glycol fluid.
Therefore, if you want a silicone based DOT brake fluid in your vehicle, then you should completely flush out all the poly-glycol brake fluid. The best time to switch to silicone based fluid is during a complete brake system overhaul.
Personally, I prefer using a single, high-quality brand of brake fluid of the DOT type specified for a particular vehicle. I always avoid mixing liquids whenever possible.
Testing of Brake Fluids
1. Equilibrium Reflux Boiling Point (Dry Boiling Point)
The Equilibrium Reflux Boiling Point is the temperature at which the fluid begins to boil when brand new from the bottle and has not absorbed humidity. When the brake fluid is tested, it should not be less than the below values for the indicated grades in degrees Celsius:
DOT 3- 205
DOT 4- 230
DOT 5.1- 270
2. Wet Equilibrium Boiling Point (Tested with 3.7% Water)
The Wet Equilibrium Boiling Point is the boiling point temperature with a brake fluid that has a 3.7% volume of water, usually after one to two years of the fluid being in use. When the fluid is tested, it should not be lower than the mentioned values as per the indicated grades in degrees Celsius:
DOT 4- 155
DOT 5- 180
DOT 5.1- 190
The most efficient way of testing the fluids is by Boil Test. The moisture tester will connect to the battery and boil the fluid present in the reservoir displaying the accurate value and a remainder of minimum values.
3. Kinematic Viscosities
Viscosity is a vital parameter for the safety of your vehicle. It directly influences the behavior and operation of the brake system and the clutch. Therefore, the brake fluid should fulfill specifications mostly at -40° and +100°celcius.
A viscometer is used in the determination of brake fluid kinematic viscosity. When the fluid is tested, its kinematics viscosities in square millimeters per given second at the stated temperatures should not be less than 1.5mm2/s at + 100°:
|Fluid Type||Kinematic Viscosity at -40°celcius (mm2/s)||Kinematic Viscosity at +100° celcius(mm2/s)|
4. pH Value
This is the value that shows basicity/ acidity in a fluid. If the value is lower than 7.0, it is acidic. Such fluid can accelerate corrosion of the brake components. When the fluid is tested, its pH value should not be less than 7.0 or more than 11.5
5. Brake Fluid Stability (High Temperature and Chemical Stability)
When the brake fluid is tested, the Equilibrium Testing Boiling Point should not change by more than 5.4° F plus 0.05° for every single degree that the Equilibrium Testing Boiling Point of the brake fluid exceeds 437° F.
When the brake fluid, excluding DOT 5, is tested, changes temperature should not be more than 5.4° F Plus 0.05° for every degree that the Equilibrium Testing Boiling Point of the brake fluid exceeds 437°F.
As the fluid ages, corrosion inhibitors present in the fluid break down. After corrosion has begun, copper traces will appear. If the copper is above 200ppm, the brake fluid should be replaced.
Brake fluid additives help in protecting metal brake components and rubber. If testing indicates contamination, a replacement has to be done. When the fluid is tested, the metal test strips should not show changes in weight exceeding certain limits.
7. Fluidity and Appearance at Low Temperature
When the fluid is tested, at the storage temperature, the fluid should not show sedimentation, crystallization, sludging, or stratification.
Upon inversion of the bottle, the duration required for air bubbles to travel to the top should not be more than the bubble flow times.
Upon warming to room temperature, the specimen should resume the fluidity and appearance it had before chilling.
8. Water Tolerance (Low Temperature and at 60° C)
At Low Temperatures,
When the fluid is tested at a low temperature, it should not show sludging, crystallization, sedimentation, or stratification. When the centrifuge tube is inverted, air bubbles should travel in not more than ten seconds to the top of the fluid.
If cloudiness develops, the fluid should recover its clarity and fluidity as soon as it is warmed to room temperature.
At 60° C,
When the fluid is tested, it should not show stratification. Sedimentation should not be more than 0.15% after centrifuging by volume.
9. Compatibility (Low Temperature and at 60° c)
At Low Temperature
When the fluid is tested, it should not show sedimentation, crystallization, sludging or stratification except DOT 5
When the specimen is tested, sedimentation should not exceed 0.05% after centrifuging by volume and should not show stratification except DOT 5.
10. Resistance to Oxidation
When the fluid is tested, metal test strips that are not in contact with tinfoil should not show visible etching or pitting without magnification. No more than a trace of gum should be deposited on test strips that are in contact with the tinfoil.
Aluminum strips should not change in mass by more than 0.05mg2/cm and cast iron strips should not change in mass by more than 0.3mg2/cm.
11. Effects on Cups
When brake cups are exposed to brake fluid, according to the test, the increase in diameter of the bases of the cups should not be more than 0.006 inches. In addition, the cups should not show disintegration as evidenced by blisters, stickiness, or sloughing. The decrease in hardness should not exceed 10 IRHD at 70 ° C.
12. Stroking Properties
When the fluid is tested, metal parts should not show etching or pitting to a visible extent without magnification. The change in diameter of the piston or cylinder should not exceed 0.005 inches.
None of the cups should be in a substandard operating condition as evidenced by blisters, stickiness, chipping, cracking or other changes in shape. None of the cups should show an increase greater than 0.035 inches in base diameter.
The cylinder pistons should not function poorly or freeze throughout the test. Total loss of fluid at the end of the test during the 100 strokes should not exceed 36mm. At the end of the test, the fluid should not show the formation of gels.
The amount of sediment should not exceed 1.5% by volume. The brake cylinders should be free of deposits that cannot be removed even when moderately rubbed with a cloth wetted with ethanol.
Brake Fluid Comparisons
DOT Brake Fluid vs. Mineral Oil
Apart from the four types of DOT brake fluids I have mentioned, there is another type of brake fluid referred to as mineral oil. Mineral oil is the rarest kind of brake fluid, used by only a number of automobile manufacturers, such as Magura, Tektro, and Shimano.
The most popular brake fluid in today’s market is DOT fluid. All the brake fluids that are regulated by the DOT standards are either poly-glycol or silicone based. There are made up of lubricants, solvent diluent, modifier-couplers, and inhibitors.
DOT brake fluids are needed to meet standards as well as specifications set out by the Department of Transportation and the Society of Automotive Engineers. These standards set out minimum boiling points and brake fluid performance that manufacturers must abide by.
On the other hand, mineral oils are brake fluids that do not adhere to any regulatory body or standards. Therefore, the technical information of mineral oil brake fluids is hard to find. Magura and Shimano are well-known for maintaining a high level of secrecy on the subject.
Unlike DOT brake fluids, minerals oil brake fluids are hydrophobic. Therefore, they do not absorb moistness from the surrounding environment. This simply means that there are no minimum dry or wet boiling temperatures to be worried about.
So, the very good news is that mineral oils are able to maintain a constant boiling point. The only problem is that any moisture that finds its way into the brake system through microscopic pores or seals will significantly relegate the boiling point of the entire system to that of water.
With that said, you should avoid substituting a DOT brake fluid with mineral oil. This is not recommended and can damage your brake system.
DOT 3 vs. DOT 4
DOT 3 brake fluid is the more popular of the two for cars and light trucks. On the other hand, DOT 4 fluid is gaining popularity because of its capability to perform in a congenial combination with traction control and an anti-lock braking system.
I find DOT 3 to be an inexpensive choice for average cars where the driver is less likely to apply aggressive braking actions. However, automobiles, such as police and racing cars that require repeated vigorous braking should use DOT 4 brake fluid.
The main difference between the two fluids is their boiling points. DOT 3 has lower boiling points than DOT 4 and is more likely to assimilate water. Therefore, DOT 3 boils easily when subjected to rough and hard braking.
This can certainly damage the braking parts and even lead to below average braking performance. If this is what you are experiencing, you should consider replacing it with DOT 4 if and only if it is completely necessary.
There is also a slight difference between DOT 4 and 3 brake fluids in their chemical structure. DOT 4 has a blend of borate and glycol while DOT 3 has a mixture of glycol and ether. The chemical components of DOT 4 have a high tolerance for high temperatures and water.
DOT 3 vs. DOT 5
There are two major differences between DOT 3 and DOT 5 brake fluids: boiling points and chemical composition. DOT 3 is glycol ether based, while DOT 5 is silicon based.
Most of the current day vehicles brake systems use glycol brake fluid. On the other hand, silicon-based brake fluids are normally found in special applications, such as show cars since they do not damage the paint surface. Not to mention that DOT 5 fluids are hydrophobic.
DOT 4 vs. DOT 5.1
DOT 5.1 and 4 are both glycol based fluids. They are broadly used in the cycle and automotive industry. Being glycol based, they are compatible and can be mixed without damaging your brake system.
The main dissimilarity between the two fluids is their minimum boiling points. DOT 5.1 has higher boiling points, meaning that it offers steadier performance during tough braking and high temperatures.
Brake Fluid vs. Clutch Fluid
If you didn’t know, these two are the same. You can suitably top the clutch master cylinder with brake fluid. However, clutch fluid is only relevant with manual gearboxes. You need to know if your car is equipped with a hydraulic clutch system.
Vehicles with a manual transmission may have a hydraulic clutch system that uses both a clutch master cylinder and brake fluid.
Depending on the vehicle, the brake master cylinder reservoir may also supply the clutch master cylinder, or the clutch may have a separate fluid reservoir.
Brake Fluid vs. Paint
Most brake fluids are likely to damage your car paint. However, if the paint is of high quality, the damage will not happen overnight.
In my experience, brake fluid takes a considerable amount of time to cause severe damage to a car’s paint. According to my findings, when I poured brake fluid on a section of my old car, it took around 24 hours to display some annoying stripes on the paint as the fluid flows.
I recorded more damage with time. It is not actually a myth; brake fluid isn’t friendly to paint. In fact, the paint on the brake backing plate can become bubbled, indicating a brake fluid leak.
Brake Fluid vs. Hydraulic Oil
There are many applications of hydraulic oil, and one of them is hydraulic brake fluid. Hydraulic brake fluid is produced using water or refined mineral oils depending on the brand. Basically, this is a form of hydraulic oil used in brake systems.
The materials used to make hydraulic brake fluids have remarkably high boiling points, making them ideal for braking. In fact, hydraulic fluid and hydraulic oil are terms that are at times used interchangeably.
Brake Fluid vs. Power Steering Fluid
Brake fluid is mainly glycol-based, it absorbs moisture into the brake system, and dissipates heat. It is the perfect choice for static brakes, but it is not a good lubricant. On the other hand, power steering fluid is petroleum-based, provides a pressure transfer medium, is used for dynamic steering, and is a lubricant for metal-on-metal contacts.
Some power steering fluid reservoirs are the same shape as the brake fluid reservoirs in master cylinders. There have been cases where a power steering fluid was accidentally installed in the master cylinder. If this happens, everything but the steel brake lines must be rebuilt or replaced. Do not use these two fluids interchangeably.
Brake Fluid vs. ATF
Brake fluid is specially formulated to convey brake pedal pressure to the wheel cylinders from the master cylinder. It is absolutely crucial to use brake fluid that is completely free of moisture or contamination.
Then again, automatic transmission fluid refers to a lubricant used in automobile transmission. Different forms of transmission fluids are needed for manual and automatic transmissions. ATFs also help transmit power, and they act as coolants.
Though, both ATF and brake fluid are necessary for the proper functioning of an automobile. This is basically the only thing that they have in common. They vary in composition, usage, and how frequent they should be changed.
Brake Fluid vs. Engine Oil
The two are different, and they should not be used interchangeably. If you mix engine oil with brake fluid, then the viscosity of the engine oil will be lessened. When you substitute brake fluid with engine oil, the results will certainly be catastrophic.
Brake Fluid vs. Water
Typically, all contemporary hydraulic systems use specialized fluids that are mostly glycol based. According to hydraulic fluids manufacturers, brake fluids are not designed to boil or degrade at high temperatures during repetitive use.
Usually, the brake system experiences constant physical and thermal stress whenever you use the brakes. Any water that gets into the system would certainly corrode metal components. Glycols found in brake fluids are effective at absorbing water in order to protect the metal parts.
Brake Fluid vs. Rubber
In the brake system, leakage of brake fluid is prevented with the use of rubber seal rings. The hardness, as well as swelling of the rubber seals, is expected to remain within given limits when exposed to brake fluid.
Basically, all glycol based fluids are expected to be harmless to healthy rubber components. What damages rubber components is the breakdown of additive packages, which control the pH of the brake fluid.
In the event that brake fluid is unable to regulate corrosive elements and pH, metal and rubber parts are likely to deteriorate with time.
Brake Fluid vs. Aluminum
Aluminum would seem to be a good material for caliper pistons because of its lightweight nature. In fact, aluminum has been used for pistons in some high performance brakes where weight is critical, but it has serious drawbacks that limit its use in passenger cars and light truck brakes.
When using glycol based fluid, inactivity may result in heavy corrosion of the aluminum brake cylinder. However, silicon based fluid wouldn’t corrode aluminum brake components. Also, aluminum is a poor thermal insulator and may increase the danger of boiling the brake fluid.
Brake Fluid vs. Coolant
Brake fluid does not act as a coolant for your brake system.
Compressibility is usually directly related to temperature. Therefore, if brake fluid absorbs any heat from the system’s disc, the fluid’s temperature will increase, so is the compressibility.
Usually, your brake system requires extremely low compressibility.
Therefore, any increase in compressibility directly impacts pressure transmission, which results in pressure losses. This would lead to partial brake failure or ineffectiveness.
Brake Fluid vs. Gear Oil
The brake system is composed of rubber seals. The rubber seals are not in any way compatible with gear oil or any other mineral-based oils. If you introduce gear oil into your brake system, you will cause swelling of the rubber seals, thus interfering with normal braking.
Do not even attempt to flush your brake system with gear oil. If you want your brake system to be flushed as well as checked for normal operation, You should simply contact a certified mechanic if your knowledge is limited.
Brake Fluid vs. Silicone
Glycol based brake fluids are hygroscopic; they can absorb water as well as function effectively. A given amount of glycol is likely to absorb a given amount of water within a given time duration. This is why you are advised to change your brake fluid at recommended time intervals.
On the other hand, silicone based brake fluids are hydrophobic; they do not have an affinity for water. Unlike glycol based fluids, silicone based are most popular with the military, vintage, and classic vehicles.
Also, glycol based are twice less compressible when compared to silicone based. So, they offer an increased pedal feel.
Brake Fluid vs. Master Cylinder
The master cylinder is a hydraulic pump. When you pump the pedal, the brake fluid will be forced into the calipers. Air, on the other hand, compresses easily, so any air present in the braking system will lower down the hydraulic pressure.
The master cylinder will not automatically bleed out the air present in the brake fluid. This needs to be done by taking it out and bleeding the air before it is mounted back.
Brake Fluid vs. Chlorine Water
Brake fluid is polyethylene glycol based while chlorine water is calcium hypochlorite. These two chemicals react violently when they are mixed together, producing a fireball. The chlorine water produces radicals that react with the fluid in a chain reaction disintegrating brake fluid glycols into flammable aldehydes and ketones.
Brake Fluid vs. Penetrating oil
Both are hydraulic fluids but have different properties and different additives. They also have lubricating properties that help in ensuring the brake system performs optimally.
Brake fluid has a high boiling point and very low compressibility. It is hygroscopic meaning it absorbs water from the surroundings.
Penetrating oil has high hydrophobicity; hence it repels water, and low viscosity, and therefore it reduces wear and tear.
Brake fluid Vs. Differential Oil?
Brake fluid transfers force into pressure to amplify braking force.
Differential oil is located in the axle housing and is designed to operate under high pressure, rather than high boiling points like the brake fluid. In addition, Differential oil has a high viscosity and is resistant to heat.
How We Chose the Best Brake Fluid
There are definitive benefits to replacing your brake fluid with a synthetic or high performance product. As discussed in this guide, the most rated brake fluids are graded based on their boiling points.
Regular fluids are fine for regular driving.
However, when you add more weight or power to your vehicle, you increase stress on your brakes, and so they need for advanced brake fluid. Regular brake fluid will hardly make it to 300°F before boiling.
But the popular high performance brands will go to about 500°F or more. The best fluid should be able to resist boiling up to 600°F or more. Over the years, performance and grade numbers set by the U.S. Department of Transportation have increased.
So, establish a baseline. Once you have done that, choose your brake fluid based on the boiling points, and whether or not you want synthetic or standard brake fluid.
Brake Fluid FAQs
What Kind Of Brake Fluid Do I Need?
There are different types of brake fluids. They include glycol-based fluids and silicone-based fluid. Silicone-based fluids are put only in vehicles with non-ABS systems. It is important you check your car manual that will indicate the best type of fluid you should buy for optimal performance.
How to Check Brake Fluid?
To check your brake fluid, you should first find the reservoir. The model of the car determines its location. Start by cleaning the top of the reservoir to prevent dirt from falling into the fluid.
The next step is to open the top of the fluid reservoir and then look to see where the level of the fluid lies against the minimum and maximum lines located outside the reservoir. If the level is not high enough, add the required brake fluid.
Examine the clarity and color of the fluid. Old fluids tend to be brown or black, and it looks like used motor oil. A dark brake fluid means you need to consider a brake fluid flush.
How Does Brake Fluid Work?
Brake fluid is called hydraulic fluid in other terms. Brake fluid works by moving components in your car’s braking system. When you step on the brake pedals, it will force small pistons inside the brake caliper, compressing and squeezing the brake rotors, slowing your car down.
Because the brake pedal does not connect to the four rotors, it depends on the use of brake lines that divert the force acting on the pedal to the four rotors.
What Happens When You Mix Brake Fluid With Chlorine?
Both brake fluid and chlorine are chemicals. When you mix the two, an improvised explosive that is made up of a fuel source-polyethylene poly-glycol brake fluid and an oxidizing agent-calcium hypochlorite will be created.
When the fuel oxidizes, the mixture will spontaneously combust, producing a fireball. This experiment should be done in closed environments such as a laboratory with safety gear and a fume hood.
What Does Brake Fluid Do to a Car’s Paint?
Your car paint and brake fluid are a bad combination. If this happens, you need to take your car to an auto body shop for repair. Changing brake fluid is a necessary step, but it can be tricky since spilling can occur. If this happens, it can eat right through the vehicle’s paint straight down to its metal.
Regardless of the number of layers of protective wax your vehicle has, spilling brake fluid on the layers will cause the paint to discolor instantly and flake off. The destruction can happen within a few minutes and may cause irreparable damage. To help avoid such a scenario, ensure the fluid is changed by a professional
What Is The Significance Of Color In Brake Fluid?
Brake fluid is white wine in color when new, but turns black or brown when old. The significance of color is to help you determine the correct time to change the oil. It is imperative you check and change the fluid regularly before it turns black or brown.
The very dark color is an indication that the fluid has collected significant amounts of contamination and has absorbed moisture.
Which Impurity Is Most Likely to Effect Brake Fluid?
There are a number of impurities that affect the brake fluid together with components. The first impurity is moisture. The fluid is hygroscopic in nature; it absorbs moisture from its surroundings. With time, moisture percentage increases, which reduces the fluid’s boiling point.
Sludge is also another impurity .with time as you operate your car, sludge will form, which may choke the brake line and increase the viscosity of the fluid. Hence extra force will be required every time when applying the brakes.
Air is another impurity that can affect brake fluid. Air acts as a vapor lock and will make the brakes feel spongy.
Is Brake Fluid Change Necessary?
Brake fluid can survive for many years as it leaves in a sealed system, but moisture from the air can work its way into the fluid and other parts. If the fluid becomes contaminated, it is capable of changing how the entire system works.
In addition, moisture can cause corrosion in calipers, brake lines, and the master cylinder. As a rule of thumb, the moisture content should be tested after every two to three years. Changing the brake fluid is necessary for your vehicle to perform optimally.
Why Should Brake Fluid Be Changed?
Brake fluid is hygroscopic in nature. This means it absorbs moisture with time reducing its effectiveness. If the brake fluid is not replaced before water content reaches 3%, the moisture will make the boiling point of the fluid drop. Hence air bubbles will be created as a result.
You probably may not be aware because the braking system appears normal until the fluid attains the reduced boiling point. If this happens, your brakes may not work, which is a leading cause of accidents.
Is Brake Fluid Flush Necessary?
Yes. Brake fluid is important for your car brakes to operate optimally. Brake fluid flushing includes removing old fluid and moisture from the reservoir and replacing it with clean, new fluid. Fluid flush is necessary as it ensures the brake system performs properly and also improves the lifespan of the brake system components.
As the ABS and traction control systems are activated, they generate heat, which breaks down the fluid. ABS and traction control components are very sensitive to moisture. Flushing is recommended before it can damage these parts.
Common symptoms that may indicate you need a brake system flush include brake pedal feeling spongy, a diminished brake system performance, and color change from clear to brown or black. Follow the manufacturer’s guidelines regarding fluid maintenance.
Is Bleeding of The Brake System Necessary?
Yes. Air in a car’s brake system has disastrous consequences not only for the brake parts but for safety reasons as well. Brake bleeding is a procedure that is performed on brake systems whereby air bubbles are removed from the brake lines.
The procedure is essential because, while the fluid is incompressible, air bubbles, on the other hand, are compressible and their existence in the brake system reduces hydraulic pressure, which can be developed within the entire system.
There are a number of methods that can be used when bleeding the brake system. Brake bleeding should be done to enable the fluid to maintain a high boiling point.
And, as always, we welcome your feedback and suggestions. Do you have favorite brake fluid? Do you have a favorite brake fluid that meets your specific requirements and budget that’s not on our list? We’d love to hear from you!
Last update on 2022-12-06 / Affiliate links / Images from Amazon Product Advertising API