JROC

Wondering what the advantages and disadvantages are to both. DOT 5.1(not to be confused with DOT 5 which is silicone based and can't be mixed with DOT 3/DOT 4/DOT 5.1) looks to be the newest thing in brake fluids and seems to have similar dry/wet boiling points as DOT 4.

Is there a good reason to use DOT 5.1 over DOT 4. I getting ready to add some 14" Brembos and would like to flush the system and upgrade from DOT 3.

Thanks,

Jesse

01ssreda4

iTrader: (96)

My strange drag brakes recommend 5.1 so that's what I use. No issues. I have no other info.

wssix99

iTrader: (5)

It must be "1" better.

01ssreda4

iTrader: (96)

DOT 4 and DOT 5.1 are both glycol-based brake fluids and are used widely in the automotive and cycle industry. They are controlled by standards set out by the Department of Transportation (DOT) - hence the name.

The main difference between these two brake fluids is in their boiling points. Part of the standards that need to be met by the manufacturers of DOT fluids are the minimum dry and wet boiling points. These are the minimum temperatures that the brake fluid must perform at before the brake fluid starts to boil, which can lead to complete brake failure.

Let's take a look at the minimum boiling temperatures of DOT brake fluid as specified by the Department of Transportation.

Remember, these are only the minimum standards. Brake fluid manufacturers can and often do improve on these figures and it is possible to find DOT 4 brake fluid with a higher boiling point than some DOT 5.1 fluids on the market.

Since DOT 4 and 5.1 are both glycol-based brake fluids they are compatible with each other, which means they can be readily mixed without harming your brake system. It is important never to mistake DOT 5.1 (glycol-based) with DOT 5 which is silicone-based and should never be mixed with any other DOT fluid.

JROC

Okay thanks for the info.

I really don't see any reason not to go with DOT 5.1 seeing as it goes for about the same price as DOT 4 from any given manufacture who sells both. To be honest even quality DOT 3 works just fine on a street car though.

pdxmotorhead

Just a sample of one,, but I find the dot 5.1 water saturates faster than the DOT4, not a big deal, but I flush and bleed it more often(every 6 month or so) than the DOT 4 stuff, It works better in my motorcycle than dot 4 fwtw..

Factory FORD heavy truck break fluid is good stuff and meets the 5.1 spec last I checked, they used to call it "Super Blue" and gallon cans were cheap..

JROC

Good info.

I ended up going with Motul RBF 600. It's a DOT 4 racing fluid with very high dry and wet boiling points. Like 594* Fahrenheit dry and 401* Fahrenheit wet. Even though it claims to be racing brake fluid (RBF) it's still supposed to be great for DD duty.

I've used Motul products for years in both my cars and dirt bikes. Good stuff. In fact Motul 8100 Eco-Nergy 5W-30 is my go to oil for my LS1. It really runs smoother and quieter with it IMO than other oils I've tried, and doesn't noticeably burn off oil.