Originally Posted By: 340_Magnum
Installed 5 quarts of 10w-30 Signature Series and a Fram Ultra XG3387 filter on my low-mile 1998 Buick Century with the 3.1 V6. The engine seems really smooth on this stuff. Previous fill was Pennzoil Ultra Platinum 10w-30.
Welcome to the Amsoil club. I have used it almost exclusively since 2004.
My wife's Wrangler had a head gasket at 165k, internals were spotless and virtually no wear, sorry don't have pics.
Noticed a 1mpg increase in mpg on my (sold) Jeep Grand Cherokee after changing to Amsoil, this was when I was driving the same 2 hour stretch of highway 2-3x a week. Also noticed a reduction in the indicated coolant temps.
Aside from my testimonials, you've already noticed a smoother engine. Amsoil can be run longer, 5k may be a little short but is good for establishing a baseline. I took our old Jeeps as high as 12k, and plan to extend on the F150 once out of warranty, or maybe earlier.