Mercedes just settled a class action because in March 2002 they sent notice that dino oil will gum up some of their engines. Synthetic is all that can be used. To me this means that there is a difference in dino and synthetic oil. Maybe in many cars it doesn't make a difference but it seems to make a difference in the Mercedes so it's not just a placebo effect to use synthetic.

 

The lawsuit was about changing the oil at 20,000 miles.

http://story.news.yahoo.com/news?tmpl=stor...630_000_drivers