DOT 3 and DOT 4 Brake Fluid: What’s the Difference? – AMSOIL Blog

The primary coil remainder between DOT 3 and DOT 4 brake fluid is their respective boil points .
I suspect I know your future interview .
But first, some background. The U.S. Department of Transportation ( DOT ) classifies brake fluid into four main categories :

  • DOT 3
  • DOT 4
  • DOT 5
  • DOT 5.1

Their primary differences are their wet & dry boiling points and their composition.

Dry Boiling PointWet Boiling PointCompositionDOT 3205°C/401°F140°C/284°FGlycol EtherDOT 4230°C/446°F155°C/311°FGlycol Ether/Borate EsterDOT 5260°C/500°F180°C/356°FSiliconeDOT 5.1260°C/500°F180°C/356°FGlycol Ether/Borate Ester
DOT 3 is the most common type used in cars and trucks today. DOT 4, however, is gaining popularity due to far-flung use of anti-lock braking systems and traction control, which benefit from DOT 4 fluid ’ s lower viscosity.

Are DOT 3 and DOT 4 brake fluid compatible?

Yes, DOT 3 bracken fluid is compatible with DOT 4 brake fluid. however, DOT 4 offers a higher boil point .
DOT 5.1 is used in high-performance and heavy-duty applications due to its high boiling distributor point. It ’ s compatible with DOT 3 and DOT 4 fluid .
DOT 5 brake fluid is silicone, meaning it doesn ’ thyroxine absorb water. It’s not compatible with the other brake fluids and is used largely in authoritative cars that remain in storage for hanker periods and need a brake fluid that doesn ’ thyroxine steep water .

Bring it to a boiling point

so, nowadays we ’ re back to boiling point. What does it mean ? After all, we ’ ra not cooking this farce .
well, in the right engage and ambient conditions, you are cooking it .
Dot 3 and Dot 4 brake fluidAggressive braking can lead to intense heat. Braking generates intense heat between the brake pads and rotors. possibly you ’ ve seen a raceway on television receiver where the producers stick a GoPro under the car to show the brakes literally glowing crimson when the driver depresses the pedal .

The intense heat can vaporize the brake fluid, causing it to become compressible, which leads to a spongy impression when you apply the brakes .

That leaves boast in the lines, which is compressible, leading to a voiced bicycle. In racing and performance-driving circles, this is known as brake fade, and it ’ s something drivers actively want to avoid. To drive as effectively and safely as possible, the driver must be confident that the brakes will perform on lap 10 as they did on lap one .
Brake fade can besides come from the brake pad/rotor interface. The pads secrete gasses, which reduces liaison between the pads and rotors. That ’ second why high-end rotors are slotted and drilled – to release gasses quicker, limiting languish .

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Brake fade isn’t just for racers

Descending a steep mound, specially when hauling a heavy load or towing a trailer, can generate fantastic heat if you ride or pump the brakes.

PRO TIP: following time, downshift into a lower gear before descending a steep ramp .

By the time you reach the bottom, your pedal may go closely to the deck, making your affection rate go about through the roof .
If you like to toss your vehicle around a curvy state road for a little therapy, standing on the brakes going into corners can create sufficient estrus to cause brake fade, besides. If you get a little excessively avid, you may end up going right through a corner and into the woods .
The fluid ’ randomness boiling point indicates the temperature at which the brake fluent zap. The higher the DOT categorization, the higher the churn period, thus the better the fluent is at resisting heat. That ’ mho why racers use DOT 4, not DOT 3, brake fluid .

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Boiling point is separated into dry & wet boiling points

The dry boiling point is determined using fresh fluid straight from a new container. The fluid ’ second wet boiling point is determined using fluid that ’ second been contaminated with 3.7 percentage water, therefore it ’ s constantly lower than the dry boil steer .

Why would test administrators contaminate dear fluent ? Because it ’ s a reflection of what happens in the veridical earth .

Brake fluid is hygroscopic, meaning it absorb water ( except silicone-based DOT 5 brake fluid ). DOT 3 fluid, for example, can absorb up to two percent water every year. moisture can enter the system when you remove the reservoir capital to add fluid, through wear seals and even through the rubber brake lines themselves. Thus the fluent ’ second wet boiling indicate is the total that more accurately represents what ’ s very going on in your vehicle .
Since brake fluid can wear out, it ’ sulfur vital you change it sporadically. otherwise, not alone will your brakes become spongy and dangerous, the moisture will slowly corrode alloy components .

A commodity convention of thumb is to change the brake fluid every other year in passenger vehicles, and at least every class in racing vehicles. The AAA says 88 percentage of motorists overlook brake care, so you ’ rhenium not alone if you haven ’ deoxythymidine monophosphate changed brake fluid in awhile, like since you bought your vehicle .

Watch now: How to bleed brakes

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It ’ randomness not besides recently to start, though. And when you do, check out our wrinkle of bracken fluids for your vehicle .
Updated. in the first place published Feb. 27, 2018 .