I don't know if this oil life test has been discussed here but I read
through the complete report and found it facinating and informative. The
test involves Mobil 1 5W30 and Amsoil 5W30 with a Firebird with an LS1
engine.
The Mobil 1 lasted 18k miles and only required a filter change at 12k.
The Amsoil test is still in progress.

Please note that the oil receives topping off as the engine invariably
consumed some as well as the small quantity lost from the sample sent
for analysis at each 1000 mile interval.

http://neptune.spacebears.com/cars/stories/oil-life.html

What is interesting is the engine wear is higher during the initial 3000
mile of the oil change and decreases thereafter.

Blackstone test lab they used have a good FAQ about motor oil.

http://www.blackstone-labs.com/faq.html

For the propeller heads this link have a huge list of reading material
of everything you want to know about oil and oil analysis.

http://neptune.spacebears.com/cars/stories/iaq.html

- Vince

http://gipsyflies.home.comcast.net
1989 Vanagon GL Camper
1993 Mazda Miata (for sale)
1996 Land Rover Discovery
2005 Mini Cooper S