Reply to "new brakes"

The drawback of DOT 5 is compressibility, it gives a more spongy pedal, not what sports car & race car drivers like. The advantage is it does not absorb water like esther based brake fluids, and it has very good high temp characteristics. BUT you cannot mix silicone based DOT 5 with the other esther brake fluids (DOT3, DOT 4 & DOT 5.1).

The absence of water absorbtion in DOT 5 fluid is a blessing and a curse. Any water that gets into a system containing DOT 5 will form steam pockets when the temperatures rise, and steam is very compressible.

DOT 4 has better high temp characteristics than DOT 3, but its performance falls off more rapidly than DOT 3 as it absorbs water, therefore systems with DOT 4 fluid MUST be flushed more often than systems with DOT 3 fluid.

DOT 5.1 is an esther based fluid that meets the DOT 5 spec for brake fluid. It is basically a modified DOT 4 fluid, so the same precautions about more frequent flushing applies. It is also much more expensive than DOT 4 fluid.

You can mix esther based fluids, DOT 3, DOT 4 and DOT 5.1 with no severe safety issues, the only drawback is the high temp properties of the fluid will vary based on the cocktail proportions.

In my opinion, a responsible auto parts supplier should not stock DOT 5 on their shelves, due to the compatibility issues with the esther based fluids.

Castrol LMA is good stuff, it has a fairly high boil point. Some racing clubs swear by Valvoline synthetic brake fluid as a low cost high performance alternative. Race suppliers like Pegasus sell brake fluids with very high boil points (higher than the DOT 5 spec).

cowboy from hell