Is it okay to mix dot 3 OEM brake fuild with dot 4 ones? A shop just did a brake bleed for my car, but we refilled with dot 4 Endless brake fuild. The mechanic said no problem, but i just want to make sure. thanks.

 

it's no problem

 

ehhh....

you CAN.. but should only be done under emergencies.. its like.. holy fck im low on brake fluid and a dot 4 bottle is the only one you have..

By mixing dot 3 with dot 4 you actually lower the boiling point of your brake fluid (means its a no no) I believe dot 4 is silicone versus dot 3 is water base.. whatever it is you can mix them but I'd bleed/flush the brakes out with either dot 3 or dot 4 if you plan to do any heavy braking/tracking..

do NOT ever mix dot 5 into anything tho...

its like "Can I top off my engine oil with non synethic even tho I'm running full synethic"..


- Eric

 

Mixing is NOT okay.

Get your system flushed and bled as soon as possible with a SINGLE type of fluid.

 

Dot 4 is NOT silicone based. Mixing is fine.

ONLY DOT 5 is silicone based and should NOT be mixed with anything else.

It would be a very bad thing if dot 3-4 were water based They are glycol based. Great stuff except for the fact that they are water absorbing.

http://www.xs11.com/tips/maintenance/maint1.shtml

 

According to the mechanic, he said Endless Dot 4 is OKAY to mix with dot 3 OEM.


If it's not okay, i will go back tomorrow and make them do a flush. How much is a regular brake flush anyway? How much if just bleed?

 

Here is a better analagy.

It's like putting 5w30 and 5w40 oil together in your car. Similar base and function, but not the same.

For maximum performance, replace it ALL with DOT 4. You're obviously looking for performance if you're putting that expensive stuff in.

 

you'll find out tomorrow

 

Mixing oils doesn't degrade it's performance depending on what oil you are putting in. A 1/2 30w and 1/2 40w isn't going to do anything

Now if the current brake fluid is more than 1 year old, then by all means, go ahead and perform a full flush. No sense in keeping the old stuff in there.

 

let's just go back to brake fuild case...

Right now, i have 50% OEM dot 3 and 50% ENDLESS dot 4. I am not going to do any hardcore braking. I just want to make sure it's safe and not going to defect my car.

 

I agree with jeff that it is completely safe to do so, but you just wasted your money on the expensive endless dot4 fluid. Your fluid mix will perform at dot3 or worse levels because it will still be the limiting factor, and since it is old the BP has already started to drop

 

Worst than dot 3 alone??? What if it's 70% dot 4 and 30% dot 3?

it's all too late now. The mechanic said it's okay during service. I just spent $90 for bleed and $35 for endless fluid.

What should I do from here? Spend another $100+ to just flush out all the 1 day old brake fluid?

 

if you paid for a brake bleed service, why wasn't all the fluid replaced?

 

the mechanic said 70% is fine.

 

would he be okay with you paying him 70% of the cost?