Scott, you didn't have to do that to calibrate the gauge. All that is required is a consistent driving style. Your car has variable lean burn modes just like my Insight -- driving with a heavy foot will knock it out of lean burn. Your gauge is likely now calibrated to an overall richer mixture so it will read low. With good driving technique you should be in lean burn for a good portion of your driving -- it will take a few tanks to get it locked in consistently and even then it may vary depending on your mix of driving for that tank. For example, P&G will give different results than steady state driving so tanks that are predominately city driving could differ from tanks which are predominately highway cruising using DWL. I use P&G in the Elantra everywhere and the calibration has been good no matter what mix I drive because of this. Good luck and enjoy your new ScanGauge!