Re: Torque spec????

Posted by Tim Cole On 2022/7/4 7:02:59

DOT 5 has a swelling agent added to mimic the effect of DOT 3 & 4. I have yet to see a manufacturer's bulletin regarding changing the brake fluid in a modern car from DOT 3 & 4 to DOT 5. DOT 5 is OEM for Harley-Davidson and AMG.

One rumor is that mixing fluids will cause problems. That is not true. When I was at DOD we found personnel mixing brake fluids with no ill effects.

As for the brake switches I had problems with those switches with modern DOT 3 which is not the same as the old stuff - that is the DOT 3 that required metal master cylinders. I did work on a 56 that came out of long term storage and had the old DOT 3 in it. I saved some of that old fluid in a vial to use as a reference. Exposed to light it turned brown. So I think those switches are responding to the new fluids.

The bottom line is that I suspect those warnings are more a legal liability issue the same way as the labels on a modern car oil and master cylinder. Motor rebuilders don't want to warrantee their work if someone is putting the wrong weight oil in their motors.