I guess if your are serious enough about the subject to do oil analysis, you've seen
www.BobIsTheOilGuy.com which is a good info resource.
According to Mobil when they addressed the issue, Mobil 1 needs far less viscosity improvers than conventional oil and that it is basicly impossible to "shear down" Mobil 1 during the use it gets in an engine. So I figure why not take advantage of the technology since I'm spending extra for synthetic in the first place and get the wider spread.
If I went back to conventional I think I would use 10-40. I had been using 5-30 in my new 2000 SE Sport until I started seeing the posts here about higher than expected engine failures and reading up on this stuff again in the past year.
My previous experience with 20-50 oil over the last 30 years (yikes) indicates the heavier stuff definately helps engines to stay tighter and healthier - I'm talking way over 100k miles which is pretty much a moot point these days when most guys keep cars for only a few years.
Cheers,
