I put on 1500 miles in 3 months. Should i change my oil at 3 months, or can i wait until 3000 miles which could be in 6 months. There have been a week at a time when the vehicle was not even started. The oil is Havoline 5w-30, and the vehicle is a 95 4.0l Jeep Grand Cherokee. Now at 1500 miles, the oil looks light brown to clear. Why the 3 month changes even if you don't have enough miles????