Eric P

GM doesn't recommend DOT4 at all , only DOT3 ... Just looking up a 94 Corvette that uses DOT3 factory when new and GM still says DOT3 , now look up transmission fluid on the same vehicle and now TSB from 2007 states use Dexron 6 that wasn't available back in 1994 yet they still say DOT3 , can you imagine the trouble I would be in if a customer had an accident and I put the wrong fluid in it , the attorney's would have a field day on me so no thanks

C3Cliff

I bought 4 SS sleeved calipers, new hoses, and a new master cylinder for my 69 in 1982. Flushed the lines with alcohol (a solvent for glycol based brake fluid) and blew the lines out with air. Put everything together and used DOT 5 fluid. 42 years so far without any leaks. I've also used DOT 5 in hydraulic clutch systems on heavy equipment such as mobile cranes where DOT 3 regularly causes problems with leaking slave cylinders. My personal opinion is that these newly discovered supposed incompatibility problems are related to improper selection of the rubber used in the seals and not some change in the chemical makeup of DOT 5 fluid. Any chemical compatibility chart you check will show that EPDM is compatible with both DOT 3 and DOT 5.