Might be a repost but anyway a few weeks ago i decided to use 15w40 instead of 1040 in the truck and Turbo T thinking oil marketing is all a brainwash anyway and perhaps the diesel stuff is the tuff stuff offering better protection. So i picked up some Lucas synthetic. Then i read this sometime ago about the testing this guy did last year. Its a good read and interesting.
http://speedtalk.com/forum/viewtopic.php?t=30483
http://speedtalk.com/forum/viewtopic.php?t=30483