A: DOT 5 is silicon based. From: "Armand Eshleman" <aje1@xxxxxxxxxxxxxxx> To: <mail@xxxxxxxxxxxx> Subject: DOT 4 Date: Tue, 24 May 2005 21:35:57 -0500 Thanks guys for bringing in some additional information about these fluids. I have a very real fear of any silicone brake fluid. In the middle 80s I was racing SCCA Formula Ford. Some of my fellow racers tried the stuff and it made the seals in their brake systems fail! This occurred during a race at speed. Very scary to be coming into a 35 mph turn at 140mph and discover you have very little to no brake. After seeing that none of us ever tried silicone brake fluid on anything. If dot 4 is better than 3 I will try that but if its silicone based I'll stay with the 3. Personally I always used AP Racing 550 fluid which functioned fantastically in the race car. Armand