DOT 3 DOT 4 brake fluid

[BumbleBee]

Hi,

My MA70 supra has written on the brake fluid resivour to only use DOT 3 brake fluid. I can not buy any high qualtiy race brake fluid in DOT 3.

The Supra is a full time circuit and drift car, I want to run better brake fluid than DOT 3.

Has anyone run DOT 4? Any problems?

I know running the wrong type can cause more harm than good?

cheers
Kris

[Hen]

My understanding is that DOT 3, 4 and 5.1 are interchangeable and mixable (and with generally increasing boiling points)
DOT 5 is a totally different makeup and not compatible with anything else.

So yes, if it specifies DOT 3 then you'll be fine using DOT 4 fluid.

[Flex]

I wouldn't interchange fluids. A car (brake system) that was designed for DOT 3 fluid would have been tested with the chemicals in DOT 3 fluid. Because DOT 4 fluid typically has different chemical composition, there could be issues if you add DOT 4 to a DOT 3 brake system.

Here's a table of different brake fluids:

Type	Boiling Temp.C	Viscosity (mm2/S)	Chemical make up
Dot 3	205	1500	Glycol Ether Bassed
Dot 4	230	1800	Glycol Ether / Borate Ester Bassed
Dot 5.1	260	900	Glycol Ether / Borate Ester Bassed
Dot 5	260	900	Silicone Bassed

[dnegative]

Mix away, it will be fine mate

[TERRA Operative]

As above, as long as you stay away from Dot 5, go as high a number as you want.

[pete05]

I just rebuilt the brakes in my Ma70 and have used dot 4 with no issues.

[BumbleBee]

Thank-you everyone. I'm going to do a complete flush and change to DOT4 race fluid

[lexsmaz]

You say you are going to run DOT 4 ( Race Fluid ) i agree with the others in that changing of Normal Brake fluid's should not be a worry as i'm sure DOT 4 wasnt around when the supra was built, but Race Brake Fluid could be another issue totally again ..

[dnegative]

Its rated as Dot 4 though, no different to a mineral and synthetic oil meeting API SM

[oldcorollas]

different chemicals tho. some say the 4 is not compatible with toyota seal materials... or ABS stuff..
but probably ok in short term (ie, life of drift car LOL )