I had a Cadillac STS that HAD to use premium due to being a high compression engine. I was told by mechanics I trusted that while throwing a tank of regular in there once in a while, like if I had no choice, wouldn't hurt anything, but over the long term it would cause a lot of problems. Loved that car but I was happy to stop paying for premium when I got rid of it.
http://www.businessinsider.com/american ... m=referral
