I see this post is just winding down, but I thought I'd throw in my .02
Jim's commentary is spot on. On more thing, you have to realize that even though the "base" stock is group III or IV it may have some lower oils as part of the add pack(sort of like filler in laundry detergent). Mobil 1 does use almost pure PAO however.
Here is my "hierarchy of oils.
Best oils you can possibly buy:
1) Motul 300V power 5w40- This oil is a di-ester(group V) with a metric @zz load of moly in it, if you have a turbo or very tight machining tolerance on a race engine, this is the oil for you.
2) anything from ELF's Excellium line, great oil with a very robust add pack.
Best oils you could buy at Local auto store or Wally world:
1) Mobil 1 5w40- (says truck and SUV on it) the marketing from XOM is horrible for this extremely good oil, easily a 10K mi service interval with this bad boy.
2) Shell Rotella T 5w40- This is a great bang for the buck, its a grp III/IV in-betweener that is billed as full syn. It's 13 bucks for 5qts and it is extremely good oil for say a 5K mi OCI.
OK I'm done for now...
