Re: Oils other than Mobil1?
Back in the mid 70's I used to talk to the Amzoil rep about using their product in older cars. I had heard that it would attack the seals causing massive leaks which he had denied. I talked to someone who had used it in their British sports car (Triumph or MG) and had the rear main seal let go, blaming the Amzoil.
'60's American cars commonly used a "rope" type seal. The problem pretty much went away with the later use of 2 piece neoprene seal. Anything past the '60's shouldn't have the seals compromised with synthetic oils.
The build up of sludge at a seal on a rotating shaft will compromise the sealing of oil as the sludge acts as sandpaper, destroying the seal.
I used to buy Amzoil from a rep who would stop by. He would test the oil in my cars and recommend leaving it in past the recommended interval. Excellent product and service.
IMO I feel the extra margine of protection is worth the price.
Art Rigsby