I have used Mobil1 0W-30/40 for the lifetime of my car. My OCI's w/ filter are 5K mi. This car sees extended runs (30 - 90 mins) of speeds in excess of 100mph on a regular basis. The car runs pretty well (26 - 35 mpg). The compression doesn't seem too good though: 185-175-165-180. Do you think there's a point in using ARX? Or is it as clean as it's going to be, given the OCI's? Thank you for any help.