You're only saving at most $3 on a full tank of gas (~ $.20 difference * 15 gallons) and that's if you stretch it to the end. If you can't afford $3 I don't see how you can even afford the oil changes.

Go ahead and use it if you want, it's not our car but typically when it says PREMIUM ONLY on the cap there's something to be said. Some people haven't had problems but they've actually seen a drop in MPG when using regular which will make you fill up more, taking more out of your pocket in the end.

You could always sell it if you don't want to pay high gas prices (which really aren't that high on a global scale).