Which brake fluid you should use in your car

Here are the differences between brake fluids and why you should use the one recommended for your car

Carmakers tell you which brake fluid to use in your car because they know the kind of heat your brakes will generate. And the differences between brake fluids comes down to their boiling point and the fluid’s propensity to absorb moisture.

Viewing the chart below you can see that DOT 5.1 has the highest boiling point. It also is less viscous than DOT 3 or DOT 4, making it the preferred choice for late model cars with ABS brakes and accident avoidance systems. If your vehicle came with DOT 5.1, that’s what  you should use to flush and top off your fluid.

On older vehicles, carmakers used 3 and 4. DOT 4 has a higher boiling point, which may make you this it’s the better choice of the two. However, DOT 4 also has a higher affinity to absorb moisture, which the chart shows reduces it’s boiling point by quite a bit.

So you should use the fluid recommended by the carmaker and not second guess their engineering decision

Can you mix different brake fluids?

DOT 3, 4, and 5.1 are glycol based fluids and can be mixed if you’re in a jamb. But you can NEVER mix a glycol based fluid with a DOT 5 fluid.

Also, you should never substitute DOT 5 for a DOT 3, 4, or 5.1 fluid and vice versa.

©, 2023 Rick Muscoplat