Contour Enthusiasts Group Archives Forums Modifications Brakes Brake Fluid--Can regular and synthetic mix?

If in doubt, read the label. Valvoline does mix with factory fluid just fine.

I suspect that you may be confusing synthetic brake fluid with silicon brake fluid. Silicon brake fluid (DOT 5) is not compatible with conventional DOT 3 or DOT 4 fluid and should NEVER be mixed.

I know of no DOT 3 or DOT 4 fluid that is not fully mixable with any other DOT 3 or DOT 4 fluid. I understand that such mixibility is part of the DOT standard.