I run sythetic blend oil in my Bonneville and the wife'* Montana. I get 2-3 mpg better than straight dino juice and no better on full synthetic. I'm wondering if there'* any published and reliable info on exactly how much of the oil is actually synthetic? Seems this kind of formula info is as closly held as nuclear launch codes, and of course, every manufacturers web page claims thier product is the best. What'* up with sythetic blend oil formulas?

What brand are you talking bout?

I typically use Castrol.

I usually run Castrol 10w30,Lucas oil stabilizer and a K&N Gold filter(H1001....I think that is the right #)

Check out www.bobistheoilguy.com for everything you want to know about oil.

Yes yes.. I"m there too.. I haven't had a chance to look for it for ya.. but thats a good place to go.. thats where I got the recommendations to run Esso XD-3'* oil.

AS for Castrol.. they recommend GC (German made Castrol oil as they're better then American made castrol.. go figure. :? I will get more info bout it when I get a chance )

I don't know where I heard this but 15% is the number that I think is the approximate percentage of synthetic oil they put in the Blend.