NONONONONONONO... NEVER use DOT5 Silicone in street driven vehicles. Never. That stuff is only for show/museum cars that are driven little or none. There are well known safety issues with this fluid in street/race use.
Valvoline SynPower Synthetic DOT4 fluid is probably the best performing fluid with a decent price. It meets or beats DOT 5.1 Dry boil spec and DOT 4 Wet boil spec. It is fully compatible with all DOT 3 and DOT 4 fluids. Pricewise it's the same or slightly more than "High Temp" DOT3 that has a high dry boil but and an abysmal wet boil spec.
DOT 3, 4, and 5.1 are all variants on the same fluid class. DOT 5 Silicone is a completely different class of fluid. The two classes should never be considered compatible or interchangeable.
As noted above, installing DOT5 Silicone requires a complete system overhaul and flush. DOT5 can NEVER be used in any vehicle with any type ABS.
Is better fluid worth it? Yes.
The main, most obvious, improvements are dry and wet boil temperatures. However, the higher DOT numbers also have stricter wear prevention and anticorrosion specifications.
Dry boil is easy. It's the boil temp of brand new fresh from the bottle fluid.
Wet boil is a bit more complicated. In short, it means the fluid can drink more water before it becomes dangerously wet. Always keep in mind, The wet spec is tested when the fluid has a bit less that 4% water in it. All DOT 3, 4, and 5.1 fluids can and will degrade below the wet boil specification as they drink more than 4% water.
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RIP Crew of Columbia. 01-Feb-03
[This message has been edited by theogre (edited 03-23-2003).]
