I will in spring. That way all my vehicles are done on the same day with the same fluid.

 

It's my understanding that DOT 4 fluid will absorb moisture faster than DOT 3. If you're not tracking your car where you would benefit from the higher boiling point of DOT 4 then I would think DOT 4 would be less desirable.

 

​​​​​​But if you flush every couple of years, I'd that an issue?

 

Has anyone tried using 5.1 fluid?

 

I would think someone would use it if they were racing. I don't know that for street use there is going to be that much more of a difference.

By FMVSS116 standards, DOT 4 brake fluids must have a minimum dry boiling point of 230°C and a minimum wet boiling point of 155°C.


BRAKE FLUID DOT 5.1 is a brake fluid for hydraulic brake and clutch systems with a boiling point of at least 260 °C and an extremely high wet boiling point of at least 180 °C. Because of the low viscosity at low temperatures, particularly suitable for additional systems, such as ABS and ASR.

 

It’s BRAKE fluid. I drive spiritedly. I bleed brakes yearly

 

I didn't notice this question from 7 months ago until the thread popped back up. As I said in a previous post there are many vehicles on the road that get by with very old brake fluid and the drivers never have a problem. However, every once in a while we hear accident reports where drivers say their brakes failed. Could those failures have been caused by brake fluid that was so old it was saturated with the maximum amount of moisture it could sustain? Brake lines are made from ferrous metals and will rust through from the inside, brake calipers are made from metal and the brake pistons in them are made from metal. Exposure to moisture can degrade those components. It is a long process that can take over a decade to reach the point of failure and the brakes will work just fine until a line bursts or a seal is unable to seal a cylinder anymore.

The cast iron brake calipers that used to be delivered with 1965 through 1982 Corvettes would rust and start leaking due to the cylinder walls rusting within a short time period unless the DOT3 brake fluid was bled regularly. Like a lot of Corvettes, these cars weren't driven often. When the brake calipers were disassembled the rust pits could be seen right where the seals sat for long periods of time. There is an aftermarket industry devoted to restoring these calipers by lining them with stainless steel inserts and changing the seals to a modern seal design that is less susceptible to leaks. On vehicles that had drum brakes, I remember having to purchase new brake cylinders or honing the existing brake cylinders to remove rust pits before rebuilding them.

Bill