This is an interesting thread, and we seem to have a couple of very knowledgable
oil guys here.
I've been running Mobil 1 for years now in virtually every 4-stroke engine I own, even my lawn mower and the diesel in my tractor.
I run 10w30 in my Explorer, with over 200,000 miles. (It still uses less than 1 pint in 5000 miles.)
I use 15w50 in the Cobra, as it doesn't get run in cold weather, and it has a pre-luber.
By far the toughest on
oil is my Legends car. Races run 30-40 miles, nearly 10,000 rpm,
oil temps nearly always over 300*, and occasionally hitting 340* (And I have one of the cooler-running setups).
I run the same Mobil 1 in there, but I change oil each race weekend, and I add 2 ounces of GM EOS to the 5 qt capacity.
I suspect the EOS is high in
zinc, which should help prevent galling of the cam lobes, which, being right up there on top of the air-cooled head, run at God-knows-what temperature.
So far I havn't seen any signs of galling, and my valve clearance has remained constant, so it must be working.
Please feel free to comment on my experiences.
Later,
P.S. Jerry,
Mobil 1 is C rated for diesels, so it would be exempt from the new restriction.
That rating is what allows me to run it in the tractor.
(I run Rotella-T in the Ford Powerstroke, as it requires a CH-4 rating due to the electro-hydraulic direct-injection system.)