Which brake fluid do I choose?

[Grouser]

Restoring my 54 Willys Jeep. All new brake lines Master cylinder wheel cylinders everything. Four-wheel drum brakes so heat shouldn't be a problem. Just wondering since I have the opportunity to use any type of brake fluid I want what's best? I'm aware that the different types generally have to do with its ability to deal with high Temps. But are there other advantages to the silicone or higher dot Fluids?

[LarrBeard]

Restoring my 54 Willys Jeep. All new brake lines Master cylinder wheel cylinders everything. Four-wheel drum brakes so heat shouldn't be a problem. Just wondering since I have the opportunity to use any type of brake fluid I want what's best? I'm aware that the different types generally have to do with its ability to deal with high Temps. But are there other advantages to the silicone or higher dot Fluids?

There are a number of questions about using newer technology fluids with old technology Jeeps. There are improvements to just about every fluid that can be put in a Jeep since the original Jeep came along, but the question is "Will I see any improvement in my Jeep if I use these new tech fluids?"

In many cases, even though the new fluids have better viscosity, lubricity, temperature stability - and so on - in many cases these improvements don't make old Jeeps work better. A prime example is synthetic motor oil; it tends to lubricate so well it just crawls past the seals in L/F-134 engines.

Silicone and High Temp DOT fluids will have advantages in many applications where higher brake system pressures and high operating temperatures are a factor.

But, and this is an opinion that doesn't have a huge body of research to back it up, in a 1954 Jeep - just about the most basic brake fluid will work just as well as the most exotic!

Here is a clip I found comparing DOT-3 and DOT-4;

DOT3 is the most common type of brake fluid used by daily drivers. You can expect to find that most cars and trucks use this type. Essentially it’s for vehicles that don’t use their braking system aggressively, i.e. don’t turn the kinetic energy into heat that DOT 3 can’t handle. DOT 4 has a higher boiling point and has found its place in racing vehicles and police cars. DOT 4 has also started to gain more popularity because of increased usage of ABS and traction control.


I suspect the silicone based fluids are just 'way overkill.

[Grouser]

If the silicone doesn't add to the survivability or corrosion resistance or anything else like that I agree. Thanks for your help that was a great read.

[gmwillys]

Corvettes have been using silicone brake fluid for around 20 to 25 years. This is not just to battle heat, but more for winter storage purposes. The silicone fluid doesn't pull moisture from the environment. If your brake system is all new, no problem, just fill with the silicone fluid. If you have used DOT 3, the whole system has to be flushed with alcohol, then blown out clean. Silicone is not compatible with any other types of fluids.

[Grouser]

sound good,,,,
but was asked if I knew the parts I was using were compatible with silicone fluids,,,,
is that an issue with this older equipment?

[gmwillys]

No issues at all.

[LarrBeard]

...The silicone fluid doesn't pull moisture from the environment...

Well, we learn something every day. I knew that the DOT brake fluids were glycol based (technically diethylene or polyalkylene glycol, not the anti-freeze ethylene glycol) and that they tended to absorb water ( they are "hygroscopic"). I did not know that silicone fluids were non-hygroscopic - and since a lot of out Jeeps sit more than they run (kind of like Corvettes), a silicone based fluid might be a good idea.

GMWillys notes the incompatibility between DOT-4 and DOT-3 fluids and the incompatibility between silicone based (DOT-5) and everything else. But, there is DOT-5.1, which is claimed to be compatible with DOT-3 and DOT-4.

I found this on the internet, so we know it has to be true ....

" A new formulation has recently been developed called DOT 5.1. This fluid is identical to DOT 5 silicone in both boiling point and viscosity; however, it is compatible in the poly-glycol based systems and anti-lock brakes as well. DOT 5.1 can be used in place of either of the poly-glycol-based fluids even though it has half the viscosity of DOT 3 or DOT 4 fluid. In fact, DOT 5.1 can be intermixed with the other non-silicone based fluids.".

If we are starting out with a new brake system or doing a really good clean and flush, silicone DOT-5.1 might not be a bad idea. It's pricey, but then we do it only every 5-years or so...

Now we can sound like brake fluid chemists ...

[bmorgil]

Definitely some good info here guy's! Thanks.

[Grouser]

Wow bet we all learned something today. That kind of fixes all the problems right there. Thanks for the info man