Road Rage

A while back, I disucssed the ins and outs of brake fluid. The short version is that it is often best to stay with the manufacturer's recommendation, as that assures compatibility with the brake components, seals, etc. Still, some want higher perf fluid, and there is all sorts of technical misinformation on Web moronathons. So, here goes another lecture from Prof Rage.

DOT3 and 4 are all polyglycol based. DOT4 adds borate esters which provide an extra buffer for the fluid against acids formed when water is heated. All glycol-based fluids are miscible with water, which is both good and bad.

Brake fluid loses its anti-corrosion factors gradually, and water is absorbed from the reservoir (plastic "breathes" a bit, which is why you should buy fluid either in a metal container or with a recent birth date on the bottle). After 2-3 years, it is shot, with risk of corrosion in the calipers and the valves in the ABS system, and about 3% water. This lowers the boiling point below 300 degrees Fahrenheit - not good.

I recommend at least every two years, regardless of mileage, or every one year if you are as anal as me. It is cheap insurance.

Racing fluids such as Motul and Ate (German, pronounced Ah-Tay) have higher boiling points, but also higher absorption rates - so do not switch unless you replace thye fluid every two years or sooner - not aporblem for racers, but not for do it once and forget it types. Ate comes in both Yellow and Blue colors, so one option is to switch between the two every change, so when the fluid color changes at the bleeders, you will know you have thoroughly flushed. http://www.spmotorsports.com/lubricants.html#ate

Valvoline Synpower has high boiling temps and is DOT4, widely available, and not highly absorptive. Ford fluid is very high quality DOT3, with a much higher boiling point than required by DOT3 spec - I think it comes in a metal can which assures stable storage life.

850EX

This is a good "Post for the week"

1999TL

What about redline?

Road Rage

What is the question? I am not aware RL makes brake fluid

1999TL

DOH! I bought Motul, not redline. Got it confused. IT's still on my bookshelf.

Road Rage

Motul products are great - for the brake fluids, follow my recommendations for "race" fluids - they need to be changed regualrly, no more than 2 years max!

OldGuy

What about DOT 5 fluids? Should Honda fluids be used or can any DOT 3 to 5 fluids be used as long your criteria of metal container and/or recent birth date is observed. This is a relevant issue for me right now as I am in the midst of doing the brakes on a fixer upper, a 92 Integra GS.

Road Rage

Stay away from silicone Dot 5 fluid - it is incompatible with Acura brake systems and will cause a world of woe. I just psted a detailed answer to a similar question on one of the Mustang forums.

OldGuy

Thanks for the tip Rage. I'll stick with DOT3.

Bitium

Thanks for the info......good to know.