I have DOT 4 and can’t get 5.1. I have no idea what fluid I added to my brakes last time they needed a bleed. Does it matter if I used 5.1 last time and add a little 4?
If it does matter, Can I simply flush the system through. I only need to top the reservoir up as I accidentally let a tiny bit too much out of the calliper last night as I wanted a little more retraction.
The DOT glycol brake fluid standards (3, 4, 5.1) specify minimum wet and dry boiling points. It’s not uncommon for some high performance varieties to be DOT4 because they have higher dry boiling points but don’t fare so well when mixed with water (but in those car’s you’d change the fluid more often so it’s moot).