Yes, while all of you are talking about adding octane with products like Torco, I am wondering what happens if you run a stock STi with regular unleaded in it. I may sound like a real a$$ to the rest of you for asking, but I swear I am asking for someone else.I am overseas in the Army and can't think of anything better to blow 30+ grand on than a STi when I come home in February, but in exchange for him paying the insurance and driving the car while I am deployed, my father the miser wants to run regular unleaded in the car. The sales lady told him he could and I've heard it's horrible. What will happen? Will the knock sensors take over and save the car while robbing power or will it seriously mess up the engine? I have also asked SOA but have not recieved a reply yet.