I guess I'm in that .1%. Reason I ask is that things change, and oil has changed and improved since the last xfire was built. Pennzoil Platinum's base oil is made from natural gas, virtually impurity/sulfur/nitrogen free, unlike Mobil 1 who's base oil is made from crude. Newer technology. I used to use Mobil 1 but my xfires seem to run a little better/smoother with the Pennzoil, and at oil changes the Pennzoil comes out looking virtually like it did when it went in. I was wondering if there are any new thoughts on the issue, or is everyone pretty much baked into "that's the way it's always been done" mindset? Most of the tests and opinions I've seen/read give the edge to Pennzoil. As to viscosity, I've read that in hotter year round climates it's best to use 5W-40 and in climates that get cooler (such as here in North Carolina and north) 0W-40 is best in xfires, and is what I use. Thoughts?