Impressive web site w/technical information on motor oils,

[benEzra]

transmission fluid, greases, and other lubricants.

www.bobistheoilguy.com

Did you know that 5W-30 is often slightly thicker than 10W-30 at operating temps, protects the engine better at startup, and often contains better base stocks? I didn't know that...

Interesting info on the science of wear and wear additives, the chemistry of synthetic oils (they're not nearly as petroleum-like as I thought, which is a good thing), specs of various motor oils at various temps, which oils are rebrands of other oils, etc. In short, more than you ever wanted to know about what oil to use in your car...