Here is a link to some field tests on Mobile 1 and Amsoil:

http://neptune.spacebears.com/cars/stories/mobil1.html

This link takes you to the Mobile 1 write-up and the menu on the left will take you to the Amsoil write-up plus other information. I don't know how scientific this is - they did use Blackstone for some of the tests. (It's been a while since I read this.)

 

got a low profile lift at work +10. oil technology has come a long way, synthetics on daily commuting is fine for 4-5K.