I wouldn't trust anything but mileage when it comes to oil changes, or if you don't drive much, then I would always change oil before storage...Mobil 1 can hold up to hard driving, high temps, very well, and could prolly be fine up to 10K between changes, but I would just as soon rely on mileage...I would recommend changing oil anywhere between 3-5K....I drive for a living and have oil samples taken between changes in the big truck. I change oil every 10K miles in the big truck, cummins motor, which can be every other month in most cases....most of the time, recommendations coming back from oil samples, are for higher mileage changes, but having good oil in there is always a good thing...