kerryg
9th September 2004, 12:45
FWIW I thought I'd share this.
Last weekend I went to Motomail to get some brake fluid. I wanted DOT3 or 4 (cos that's what the manual says) and they didn't have any. The young man who served me said (I'm paraphrasing him but the gist of it was) "we don't stock DOT 3 or 4 cos this [pointing to bottles marked DOT 5 and DOT5.1] supersedes it". I was not sure so decided not to buy, having in my mind some nagging worry about some brake fluids not being compatible.
I did some research and it seems the young guy was right...PARTLY. The DOT5.1 is glycol based chemistry that can substitute for DOT3 and 4 (also glycol based), no problems, BUT (it's a biggish but) DOT 5 is different. It's silicone chemistry and is not compatible with/miscible with the glycol based fluids.I don't know what risks (if any) might result from mixing the two but it seems a bad idea to me (like oil and water, they stay separate).
Last weekend I went to Motomail to get some brake fluid. I wanted DOT3 or 4 (cos that's what the manual says) and they didn't have any. The young man who served me said (I'm paraphrasing him but the gist of it was) "we don't stock DOT 3 or 4 cos this [pointing to bottles marked DOT 5 and DOT5.1] supersedes it". I was not sure so decided not to buy, having in my mind some nagging worry about some brake fluids not being compatible.
I did some research and it seems the young guy was right...PARTLY. The DOT5.1 is glycol based chemistry that can substitute for DOT3 and 4 (also glycol based), no problems, BUT (it's a biggish but) DOT 5 is different. It's silicone chemistry and is not compatible with/miscible with the glycol based fluids.I don't know what risks (if any) might result from mixing the two but it seems a bad idea to me (like oil and water, they stay separate).