I saw M1 0w40 at autozone at $4.79/qt, case price. I also noticed some threads on M1 oils excessively thinning on the bobistheoilguy site. So the cost of 0w40 comes to $24 for 5 qts vs. $18 for the 10w30 from WalMart in the 5 qt jug. So the 0w40 is about 35% more expensive than the 10w30...
Just did a quick drain & fill w/ Rotella T synthetic yesterday. That stuff kind of stinks compared to Delvac 1 (kind of like gear oil; the used D1 has a similar odor, but not as strong as that of the new Rotella). I remember there was a thread on the bobistheoilguy site regarding the odor that...
Don't forget that German-made Castrol-Syntec 0w30 that everyone on the www.bobistheoilguy.com forumn raves about. I've yet to see it on a store shelf. Might be more common in certain parts of the country.
-Jim
Problem w/ the M1 10w30/5w30 is the viscosity is kind of thin compared to the m1 0w40, M1 Delvac 5w40, or Rotella T syn 5w40. The latter three have comparable viscosities. I guess an economical way is to run the 10w30 in the fall-spring, then 15w50 in the summer, but I don't like having to stock...