DOT 3 vs DOT 4 Brake Fluid

[smlobx]

Yeah if I'm cooking the brake fluid, I'm doing it wrong or over driving the capabilities of the Gladiator.

Ha! Next we’ll be talking about about adding an adjustable brake bias valve to our Jeeps!

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[g2020]

3, 4 and 5.1 are compatible to mix.

In 2023, I had the brake fluid changed in my Gladiator at my local dealer. Although I wanted them to use recommended DOT 3, they used DOT 4 as a matter of course.

In 2026 (this year), I requested DOT 3 at my selling dealer, but they said that they could not go back to DOT 3 and installed DOT 4.

Unless I push Google AI hard on this issue, it tells me that I should never go back to DOT 3. I understand that additives give DOT 4 a higher boiling point. However, both are glycol based and compatible. Even if I tell Google AI that DOT 3 is recommended for a Gladiator, it says that DOT 3 will boil over if I switch back to it. I am aware that Google AI just aggregates what's written. In many cases Google AI is just flat wrong, but in this case I don't know.

I can't see how DOT 3 will boil over if I never go off road and never tow a trailer / haul heavy loads. I want to switch back to DOT 3 because it lasts a bit longer.

Question: Can you tell me if switching back to DOT 3 will be "dangerous"?

Here are my notes:

Standing guidance: Never switch from DOT 4 to DOT 3​

• DOT 3, glycol based, hygroscopic, recommended in owner's manual, appropriate for normal driving
• DOT 4, glycol based, more hygroscopic, acceptable option in owner's manual, appropriate for off-road or trailer towing
• DOT 5.1, glycol based, most hygroscopic, not mentioned in owner's manual, appropriate for track use (racing)

- Hygroscopic means that it absorbs water over time, which means a more hygroscopic brake fluid needs to be changed more frequently​

- DOT 5 is different from DOT 5.1 and is not compatible​

 

[Sweetums]

First, there’s a difference in “dry” boiling point and “wet” boiling point. Dry is the brake fluid straight from a sealed bottle, wet is once it’s started to absorb moisture from the environment - the important measure is the wet boiling point., not how fast it absorbs water.

if you are serious about high wet boiling point use Castrol SRF. I have to use it in the rear brake of my Multistrada due to some very Italian engineering and the heat interface between the rear brake and exhaust. It runs about $100/quart.

 

[Rusty PW]

First, there’s a difference in “dry” boiling point and “wet” boiling point. Dry is the brake fluid straight from a sealed bottle, wet is once it’s started to absorb moisture from the environment - the important measure is the wet boiling point., not how fast it absorbs water.

if you are serious about high wet boiling point use Castrol SRF. I have to use it in the rear brake of my Multistrada due to some very Italian engineering and the heat interface between the rear brake and exhaust. It runs about $100/quart.

I use the Castrol SRF in my Nismo. Since I have a couple of bottles of it. I use it in my other vehicles.

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