Brake fluid dot 4: DOT 3, DOT 4, DOT 5.1 AND DOT 5 BRAKE FLUID A

Brake fluid dot 4: The car’s braking system is a important system for adjusting the velocity of motion of the car, or slowing it down, or stopping it. A brake fluid is a particular fluid that ensures efficient braking energy by transferring the pressure from the brake pedal to the brake pads. It additionally has lubricating and anti-corrosion properties that enhance the performance and efficiency of the brake system and prolong its helpful life. All of those options make brake fluid choice an particularly necessary job in car upkeep.

Several types of brake fluids are tailor-made to the necessities of particular brake techniques. The most typical ones used at present are DOT 3, DOT 4, DOT 5 and DOT 5.1 brake fluids.

Are all brake fluids the identical? If not, what’s the distinction between these particular fluids?

Right here’s what it’s essential to know.


The braking system is a mechanism with excessive working temperatures. That’s the reason the brake fluid must possess sure traits to be able to meet these situations. As well as, its foremost options embrace:

For efficient pressure switch

Low viscosity – For compatibility with ABS

Lubricity – To lubricate seals

corrosion – To guard brake system elements

Excessive boiling level – To withstand excessive temperatures and never vaporize, which that have an effect on the switch of braking pressure.


DOT is an abbreviation for the US Division of Transportation. Moreover, it signifies the grades of brake fluid specified by the Federal Motor Car Security Requirements (FMVSS), or DOT 3, DOT 4, DOT 5, and DOT 5.1.

Different classification names for a similar grades of brake fluid are the J1703, J1704, and J1705 requirements revealed by the Society of Automotive Engineers (SAE) and courses 3, 4, 5, and 5.1 of the Worldwide Group for Automotive Engineering commonplace ISO 4925. requirements.


Brake fluid consists of solvent (60-90%), lubricating brokers (5-30%) and components (2-5%). As well as, brake fluid components embrace corrosion inhibitors, which forestall corrosion of steel components within the brake system, and antioxidants, which forestall solvent breakdown and deposit formation.

DOT 3 makes use of glycol ether as a solvent and a traditional brake fluid utilized in automobiles produced as much as the Nineteen Nineties. It’s appropriate for all brake techniques and all driving situations.

DOT 4 brake fluid makes use of glycol ether and borate ester compounds that enhance its efficiency in comparison with DOT 3. Automobiles constructed after 2006 use it as commonplace. Like its predecessor, it’s appropriate for all braking techniques and driving situations.

DOT 5.1 brake fluid makes use of glycol ether and borate ester compounds, however has improved efficiency over silicone-based DOT 5. We are able to say that it’s a silicone-free model of DOT 5 however suitable with kinds of DOT 3 and DOT 4 braking techniques and fluids.

All glycol-based brake fluids should be dealt with with care as they’ll injury the paint on the car or bike.

DOT 5 is a silicone-based fluid which makes it incompatible with anti-lock braking techniques. Additionally, DOT 5 can’t be blended with different kinds of brake fluids and, not like different fluids, it doesn’t hurt paint.

This fluid is designed for demanding functions corresponding to navy automobiles and very chilly climates.


Sure, however with sure exceptions.

Brake fluids will be blended provided that the fluid you add to the system is of a better grade.

For instance, a braking system that has a DOT 3 brake fluid specification might use a DOT 4 or DOT 5.1 fluid. Additionally, a system with a DOT 4 will be recharged with a DOT 5.1 with out purging the system.

Nevertheless, by no means fill a DOT 4 system with DOT 3 brake fluid. DOT 3 will be unable to satisfy the temperature necessities as a result of its decrease dry and moist boiling factors.

Once more, don’t combine DOT 5 with another kind of brake fluid as a result of its silicone-based composition.

For optimum brake system and brake fluid efficiency, it’s best to bleed the brake fluid and change it with recent.


Dry and moist boiling factors are what distinguishes brake fluids. Extra particularly, they discuss with the temperatures at which brake fluid boils underneath working situations.

The dry boiling level refers back to the temperature values ​​earlier than the brake fluid turns into contaminated or absorbs moisture. The moist boiling level represents the traits of the fluid after a sure time within the system and uncovered to atmospheric situations.

DOT 3, DOT 4 and DOT 5.1 brake fluids. They’re hygroscopic, or take up water, which is why brake fluids have two boiling factors. Then again, DOT 5 is a extremely hydrophobic silicone formulation, that’s, it repels water, which makes its boiling factors extra steady (260 °C dry boiling level and 180 °C boiling level in moist).


Most car producers suggest altering the brake fluid after 2-3 years or 30,000-40,000 km. Due to this fact, you will need to word that these values ​​differ by producer. That’s the reason it’s at all times a very good apply to observe the producer’s suggestions.

What occurs in case you use the unsuitable fluids in your automobile?

It’s not unusual for individuals to combine or use the unsuitable fluids of their vehicles, and in the event that they do, the outcomes can vary from irritating to lethal. Shopper Reviews outlines the potential injury you are able to do to your automobile—or to your self—in a narrative that seems within the November situation.

“Including antifreeze to the windshield washer reservoir might create a slimy mess,” mentioned David Champion, senior director of the Shopper Reviews Auto Take a look at Middle in East Haddam, Connecticut. “However a British well being research discovered that filling the tank with simply water creates a very good breeding floor for the micro organism that trigger Legionnaires’ illness. Shoppers ought to verify their proprietor’s guide earlier than filling any fluid underneath the hood of their automobile,” Champion mentioned. Individuals ought to verify with a mechanic, and even the oldsters behind the counter on the native auto components retailer, if they’ve any questions.

The story seems within the November situation of Shopper Reviews, which fits on sale Oct. 5. It’s also accessible to subscribers of Up to date day by day, is the go-to website for the newest automobile evaluations, product information, breaking information blogs and automobile shopping for data.

Right here’s what might occur in case you use the unsuitable fluids:

Engine oil slippage. The model of motor oil issues little, however its viscosity grade (10W-30, for instance) is necessary. Use solely what’s specified within the proprietor’s guide. Utilizing the unsuitable oil can lead to lowered lubrication and shorter engine life. If the guide says to make use of artificial oil, achieve this. Opposite to what some imagine, including artificial oil to common oil won’t hurt the engine, however there may be additionally no profit to doing so.

battery fluid. Some automobile batteries have accessible particular person cells which will should be recharged with a little bit water to cowl the lead plates. Use solely distilled water, which doesn’t comprise salts or minerals. If faucet water is added to a battery’s electrolytic fluid, it might probably enable minerals within the water to construct up on the battery’s inside lead plates, which can scale back battery energy and shorten battery life.

Be cool with the water. A automobile’s cooling system makes use of a combination of water and antifreeze; appropriately known as coolant, in concentrations (usually 50/50) designed to maintain you from freezing on a chilly day and boiling over on a sizzling one. Including an excessive amount of water to the combination could make it extra prone to freezing and boiling. That may forestall the automobile from beginning when it’s very chilly and may trigger overheating in hotter climate. Faucet water might additionally trigger mineral buildup within the cooling system, lowering its effectiveness.

Including diesel gasoline to the tank of a gasoline automobile. This can trigger the motor to stumble and knock, if it runs in any respect. Fortuitously, diesel pumps have outsized nozzles, so it’s onerous to make that mistake. Relying on how a lot gasoline is added to a diesel car’s tank, it might trigger little or no injury to the gasoline pump, injectors, and different components. If the mix-up is caught early sufficient, a technician can restrict the injury by draining the contaminated gasoline. In the meantime, don’t run the engine.

Particular sauce to your brakes. Brake techniques use hydraulic fluid that’s specifically formulated for that objective. Changing transmission or energy steering fluid, that are comparable to one another, can have an effect on the seals, injury the system, and presumably trigger brake failure. Needless to say in case your brake fluid is low, your car most likely wants brake system service anyway. Both the brakes are worn or there’s a leak.

Caught gears. Computerized transmissions ought to solely use fluid specified by the automobile producer, corresponding to Normal Motors’ Dexron sequence or Toyota’s T-type. Utilizing the unsuitable fluid could cause poor lubrication, overheating, and presumably transmission failure. A mechanic might not be capable of reverse the injury, even by flushing the transmission. Including motor oil or brake fluid by mistake also can destroy your transmission.

Plus no-nos of washer fluid. Along with creating the proper surroundings for lethal micro organism, water doesn’t clear in addition to windshield washer fluid and is topic to freezing. Using family glass cleaners or ammonia can depart foam on the windshield, injury the automobile’s end, enter the air consumption system and create a probably dangerous cabin surroundings.

Why does the brake fluid go dangerous?

Brake fluid is hygroscopic. Which means it likes water, like a sponge. Actually, brake fluid is infamous for absorbing water.

Widespread brake fluid testing units in the marketplace solely check for moisture within the fluid. Right here comes the catch: Even in case you do all the things in your energy to forestall moisture absorption, you possibly can nonetheless run into issues. Brake fluid can take up moisture in plenty of methods: by way of the packaging course of, whereas being poured into the reservoir, and even by way of the brake fluid traces.

How dangerous is “dangerous”?

Since brake fluid is hygroscopic, the required exams simulate actual world area situations.

One of many key check parameters is the boiling level of the brake fluid. Moist and dry boiling factors are examined to assist talk the standard of a brake fluid. Try this submit for extra data, however right here’s a fast overview of boiling factors:

Dry Boiling Level (ERBP): Measures the boiling level of recent liquid straight from the bottle earlier than it has been uncovered to and contaminated by the humidity.

Moist Boiling Level (WERBP): Measures the boiling level of a fluid after it has had time to soak up moisture from its environment, much like the situations by which a mean car operates (3.7% water contamination, to be actual).

AMSOIL DOT 3 and DOT 4 Artificial Brake Fluid is particularly designed to carry out in moist situations. With a moist boiling level of 368°F (187°C), it far exceeds the minimal necessities of 284°F (140°C) for DOT 3 fluid and 311°F (155°C) for DOT 4 fluid

How lengthy does brake fluid final?

Below preferrred situations, an unopened bottle of brake fluid will final about two years. It’s best to make use of a brand new bottle of brake fluid every time you want it as a result of the fluid attracts moisture as quickly as it’s opened.

As soon as in your car, the helpful lifetime of brake fluid relies on the appliance by which it’s used. Working situations, and subsequently fluid life, fluctuate relying on the surroundings, kind of kit, and software.

In excessive humidity areas, moisture is absorbed by way of the hoses and seals. Racers change their brake fluid extra ceaselessly because of the considerably increased working temperatures. As much as that time, dry boiling level tends to matter extra. That’s why we formulated AMSOIL DOMINATOR® DOT 4 Racing Brake Fluid to ship a powerful dry boil level of 580°F (304°C).

Can I combine brake fluids?

“DOT 4 and DOT 5.1 are glycol-based brake fluids and are broadly used within the automotive and bicycle industries. They’re managed by requirements set by the Division of Transportation (DOT), therefore the identify.

The primary distinction between these two brake fluids is of their boiling factors. A part of the requirements that DOT fluid producers should meet are minimal dry and moist boiling factors. These are the minimal temperatures your brake fluid should function at earlier than the brake fluid begins to boil, which may result in full brake failure.

Keep in mind, these are solely the minimal requirements. Brake fluid producers can and sometimes do enhance these numbers, and it’s attainable to seek out DOT 4 brake fluid with the next boiling level than some DOT 5.1 fluids in the marketplace.

Since DOT 4 and 5.1 are glycol-based brake fluids, they’re suitable with one another, which implies they are often simply blended with out damaging the brake system. It is very important by no means confuse DOT 5.1 (glycol based mostly) with DOT 5 which is silicone based mostly and will by no means be blended with another DOT fluid.

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