I'm just about to re-assemble my '69 396 with Muncie 4 speed. In my 4th gens, I have been using synthetic fluid in everything and I would like to do the same in the '69. I'm speaking of Mobil 1 75-90 for the Muncie and the 12 bolt posi, synthetic for the power steering and brake fluids, and of course, Mobil 1 for the engine and Dexcol antifreeze. Anyone have experience or know of reasons why the "old stuff" won't perform well using synthetics. Thanks alot.
I don't see any reason why the synthetic should not work. I recommend it to all my customers, and have it in everything I own. It meets all the GL specs and should perform the same, but protect even better than the regular lubes.
Advanced Automotive Machine
I agree, use it. I have been using and selling synthetic oil since 1977. I have it in my 1964 Impala, tranny, engine, rear axle, power steering, gear box. I also changed my 1999 GMC Sierra Z71 Extended Cab SLE over to everything by the ATF. I plan on doing that but it takes almost twice as much to flush the old out. My preference is AMSOIL, I have not used Mobil 1 since 1977 when it first came out.