All of the respectable car mag articles (I've read) on conventional vs synthetic oils conclude that little if anything is gained by using the more expensive synthtics. The one exception is for exceptionally COLD weather. Synthetics don't stiffen up as much.
Radical claims of increased MPG's or performance by an oil Co. are generally made by salesmen...not engineers.
Good oil is cheap and easy to change. It doesn't breakdown..it just gets dirty.
Having said all that.. I just put 5-30 Castrol Syntec in my Prius at 10K miles. OK..so I'm a pushover for a pretty car... The Prius ICE stops and starts a lot so I figured..what the heck..
2004, White, full package.
Castrol Synth. oil @ 2500 miles.
Hey.. \"it's just a car...\"