Switch from DOT 4 to DOT 5...problems?

[Apogee]

I've never heard of DOT6 fluid either aside from the article JP linked to mentioning that it would've saved some confusion if they had gone that route instead of DOT5.1. The DOT only rates a fluid based on it's dry and wet boiling points, hence DOT5 and 5.1 fluids have similar temperature ratings and are thus classified similarly. They however are completely different from a chemical composition standpoint, glycol based versus silicone based. Racing fluids that exceed the DOT5.1 ratings are not typically geared towards street use and as such, don't typically claim any DOT standard from what I've seen, only a temperature rating. That said, none are silicone based to the best of my knowledge due to it's tendency to readily aerate.

I've read the the US military is the number one consumer of DOT 5 silicone brake fluid due to it's better lubricity at extremely low temperatures. That said, I've also heard that they've been looking for better alternatives almost as long as they've been using it. The only OEM that I can think of that uses DOT5 fluids from the factory is Harley Davidson...not sure what their reasoning is to be quite honest, but I would guess that it has to do with it not eating paint, similar to why a lot of hot rod guys use it.



Tobin
KORE3