I have used nothing but Shell V Power in mine and notice that all Shell stations are not the same. The best Shell V Power Premium near you is at the corner of Harwood and Norwood drive in Bedford.
You need to reset your fuel octaine tables and use nothing but the best from now on, yes it is a little more expensive but at 13 or so gallons even at .20 cents per gallon more...thats just pocket change.
2010 2SS/RS A6 L99 Born 09/16/2009 Vin#9146985
ModernCamaro Car of the Month Jan 2013
CAI,Axle back exhaust, V Max Throttle Body