Price - Dot 4 and Dot 3 are compatable, but once mixed will take on the properties of Dot 3, which has lower performance characteristics. As long as you're not racing, it won't matter. Alan On Thu, Oct 20, 2011 at 12:28 AM, R. Price Lindsay <rplindsay at comcast.net>wrote: > Are these compatible? Can I mix the two? > > Price Lindsay > > 630-841-6300 Cell