http://neptune.spacebears.com/cars/stories/mobil1.html
Mobil 1 test and analysis I found interesting. Of particular interest to me is this statement:
"Engine wear actually decreases as oil ages. This has also been substantiated in testing conducted by Ford Motor Co. and ConocoPhillips, and reported in SAE Technical Paper 2003-01-3119. What this means is that compulsive oil changers are actually causing more engine wear than the people who let their engine's oil get some age on it."