THE BEST SIDE OF COSTCO GAS QUALITY

I use Chevron 99% of the time. I have not tested another manufacturers for comparison in my M5. Several years in the past I owned a GM V6 which was quite picky about the fuel I employed, and I did check the effectiveness variants with unique gasoline makes.I have never viewed an issue with the M5 or my X5M (fingers crossed, knock on Wooden), but I