welp seems that good ole exxon is trying to screw people around here...got gas sat, noticed today when i was cruising at low rpms and would give it throttle, it would detonate...never done that before i got the gas sat, and got gas at a different place than normal where they have all 3 grades comming from one pump, best guess is that they are selling 87 for the 93 price..BTW i have the xcalibrator with an aggressive tune than requires 93...