wow... so i guess i am not the only one... i religiously put BP Ultimate, and when I first got the car, I noticed in the little window of the pumping nozzle, it was cristal clear. I never looked again. THEN... my car started knocking, and every time I pump gas, I notice the gas is no longer clear, but rather yellowish. I took it to the dealer, and they said that "I was putting cheap gas". the though that they may not be actually putting ultimate in the tanks actually did cross my mind. I am going to take it to another dealer soon.