About 3 months ago I switched everything from Mobil 1 synthetic to Royal Purple and what a difference in all my vehicles. Smoother running a little better gas mileage and a little cooler as well. They state that there oil is 400% better film strenghth than the nearest synthetic competitor. I like it but is is expensive. What do you guys use and why??

In my vehicles I've always ran Mobile 1. In my boats I've ran Valvoline "Racing" straight 60 wt.
If what you say is true about royal Purple I mught justswap brands.
On a side note...Did you ever find "Blue Nun"?

Thought ya' ran astrolube

Valvoline Racing 50w . I was thinkin about switchin to the purple.

-beerjet-

Well I never found the Blue Nun . I think the Royal Purple is worth it's weight in gold and if there B.S. is true other stuff does not come close. I have alot of drag race friends that swore by it and have dyno sheets and bearings to prove this stuff is good. The only bad part is the XTR I think they call "extreme performance" for racing marine etc. is $12.99 a quart but with tripled oil change intervals and better protection I call it cheap insurance. Thanks Guys