I have a 2002 GTI 1.8T w/ the 180 hp engine. I know 91 octane is recommended, but I've been using regular gas every other tankful, and can't really feel any sort of difference in the power delivery, knocking, or any of that sort of thing. Can I get away with this, or am I doing damage. My understanding is that the computer in the engine helps adjust it to the gasoline I use. I used to use 87 in my '93 ford taurus sho with no major probelms, although 91 octane was recommended.