The owner of a 55’ Ford Sedan just sent us a note asking why we don’t recommend using DOT 5 brake fluid with our brake kits. Chances are good some of you are asking the same question, so this post is designed to clear up confusion about the different types of brake fluid.
If you cruise over to the local auto parts store, you’ll see all kinds of brake fluids in the aisle. DOT 3 is always the cheapest option—DOT 4 is about 50% more expensive than DOT 3 and DOT 5 is about two times more expensive than DOT 4. Some owners mistakenly assume that the higher cost of DOT 5 equates to better performance, but this is not always the case. In fact, sometimes the exact opposite is true. To get a better handle on why we don’t recommend DOT 5 for our brake kits, we need to take a crash course in chemistry.