Actually California only has 20 refineries, but then who is counting......We have 22 refineries here in California. I ran one tank of premium through, and, although I thought is smoothed out my tranny's slight start-from-stop shudder, I didn't notice a difference in anything else - but I don't flog it anyway. I'm back to regular and I don't even notice any difference in the shifting.[sleep]
I went and read the owners manual and it recommends using 87 Octane Regular Unleaded gas. To me it makes absolutely no sense to use anything other than Regular Unleaded. By using Premium you are gaining nothing other than spending more money for something that the engine has to compensate (de-tune) for. If you think Premium Unleaded gas has anything more in it than Regular Unleaded (other than more Octane) then you have bought into the gas companies hype.
I will agree that there is a difference between brands, but no difference between any one brands Regular gas versus their Premium gas other than the octane rating.