Nor anything petroleum based in a brake or hyd clutch system. The "oils" break down all of the rubber componets in the system, ie: o-rings, cups,rubber hoses, ect. Causing them to swell/disform. Can cause catistrophic failure in a brake system. Requiring replacement of the entire hyd system and flushing the steel lines completely. Dave, I hope it wasn't an ABS system. I had a customer a year ago put hyd fluid in the brake master of a new pickup and it cost him over 3 grand to fix ( and no warranty wasn't going to cover it) heh...heh.! I should'nt laugh, but, as allways it was one of the "smarter car guys"