Hummer H2 - As above guys, it says DOT3 on the filler cap and I have gallons of DOT4 spare. Can I mix the two or stick to DOT3. Any help/advice appreciated. Thanks in advance.

 

Yes dot 3 and dot 4 are compatible. Dot 4 is even better. It has a higher boiling point than dot 3.

 

They may mix chemically, but if I recall correctly, DOT 4 is more prone to moisture contamination. There is a very detailed writeup on this on one of the other Hummer boards. Sorry, but I do not have a link to it right at hand.

 

Thanks guys for the reply. I was really hoping to use what I had, but will look into it. Thanks again.

 

DOT 3 and DOT 4 brake fluids are essentially the same except for their respective boiling points. They can be mixed with no adverse effects. You would be better off to bleed and flush your system and go to all DOT 4 if that is what you have. Brake fluid does get old, carries moisture, etc after time/use.