Running premium fuel in a car that does not need high octane fuel (non turbo/super charged) is just throwing money away. 'Premium' doesn't necessarily mean better in this case. If your car needs premium it will be written under the gas door or on the speedo.

If you're worried about crud in your motor, on your next tuneup ask the shop to use a product called seafoam. It will clear your motor of carbon deposits and let the motor run more efficiently.