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Discussion Starter · #1 ·
Quick question. I know the brakes use DOT3 stock, I assme the clutch does as well? I have an upgraded clutch, shound I just make the move to DOT4, anyways? It's a daily driver.
 

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T88 YOU
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dot4 is not a better/stronger fluid than 3, it will not be upgrading at all... DOT4 has a slightly higher boiling point but different characteristics as far as seal swell and such go, i would not change it from what is originally used in it. for example, DOT5 is silicon based and if mixed with dot3/4 it will make a gummy residue and harm braking performance.
 

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Discussion Starter · #3 ·
I know the boiling point is higher, so if I plan on bleeding the system, which I need to do, any reason NOT to move to DOT4?
 

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T88 YOU
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yes, depending on the type of dot4 you use, it could have problems mixing not only with the residual dot3 fluid but could also affect the seals in the system. i would stick with dot3 if that is in fact what the stock clutch system uses, i am not sure. if it uses dot4 then yes, go ahead and use dot4. just my .02
 

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I believe I use Valvaline synthetic which is possibly dot 5. Just bleed your system of the old stuff.
 

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DOT 3 or 4 will be OK. They are compatible and mix together fine. DOT 4 has a higher boil point (not needed for clutch) than DOT 3 but also has a higher moisture absorbancy rate. Valvoline synthetic is designated as DOT 5.1 fluid and is compatible with DOT 3 and DOT 4. DOT 5 is incompatible with all of the above. It is a silicone fluid and is not recommended for any application on the Supra .
 

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just like normore said, you can mix 3 and 4 but not 5. just put dot 3 back in there, there no need to "upgrade" your clutch fluid, i doubt it will ever see high temps like your brake system does.
 

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like i said guys, dot3 and dot4 are designed to be compatible but then again it will also depend on the brand x dot3 and brand y dot4, i wouldnt mix them.
 

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Discussion Starter · #9 ·
normore said:
DOT 3 or 4 will be OK. They are compatible and mix together fine. DOT 4 has a higher boil point (not needed for clutch) than DOT 3 but also has a higher moisture absorbancy rate. Valvoline synthetic is designated as DOT 5.1 fluid and is compatible with DOT 3 and DOT 4. DOT 5 is incompatible with all of the above. It is a silicone fluid and is not recommended for any application on the Supra .
Thanks! I got some Valvoline synthetic since it said it's compatible with DOT3 and 4, and I plan on flushing my brake system soon as well, so I'll use it there, too.
 
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