How often should we be changing the oil? We drive mostly highway miles with little or no traffic and live in sunny southern california. I thought it should be on schedule B, which would be every 5000 miles. When my wife took it into the dealer for its first oil change they said it needs to come in every 3000. She didn't ask why. Are they BS me to get more money or should we be changing the oil every 3000 miles, which would be almost once every 6 weeks since she drives 500 plus miles a week.