I've had no engine issues with my 98 GT that is currently at 114,000 miles. I've run GC, Amsoil S2k, Amsoil ATM, Mobil 1 and Royal Purple. My best UOA came from GC, but they all were fine really.
Two miles per gallon form the u0bend? I've never heard of that type of result. The u-bend is...