The octane level required by our engine has nothing to do with the horsepower, it's all about the compression ratio, which is about 10.5:1 If i remember correctly. I strongly suggest everyone follow the premium fuel requirement, unless you want to pay through the nose for a new catalytic converter or other various engine/exhaust system parts. I'm sure your warranty will be voided as well, since you didn't follow the fuel requirement. For more information on what Octane is see here: http://auto.howstuffworks.com/question90.htm[/url]