Re: Mixing Yellow and Red Brake Fluid = Disaster?

DOT 3, DOT 4, and DOT 5.1 are all glycol based fluid and can be mixed. The main difference between the fluid is the boiling point. DOT 4 and DOT 5.1 are much harder to find in the stores here in the US as the domestic manufactures all specify DOT 3.

DOT 5 (silicone based) is a different type of fluid. Silicone and glycol fluids won't mix and would seperate if combined in a system. Although not likely to happen, if mixed, it would not cause any damge or malfunction to the brake system.

OP here. Yes, there was red brake fluid at one time. I still have a can of it, and it is DOT 3.

Mixing diff TYPES is dangerous, yes, but I think I am OK because the red (old) is DOT 3 (or maybe DOT2) and the new (yellow) says it is DOT3 fluid and is "DOT2 compatible".

DOT 2 fluid should be disposed of immediately. It doesn't have a high enough boiling point for disc brake systems. Besides that bottle of DOT 2 is so old it is most likely saturated with water.

Been in automotive since I was literally old enough to walk....and since 67, I dont recall red fluid unless it was contaminated...