It's been a while since I saw gas prices closer to 3 USD. I was hoping it would stay this way for a while, but it looks like it went back up again. I've always wonder why there are three octane rating for gasoline. Why not sell only two? I am sure I can probably find out if I want to, but I haven't had the chance. I guess it isn't very high on my list of things to find out. Do you happen to know what it means?