it is not just for oil changes. it is a light that comes on every 7500 miles since it was last reset. it is there to remind you that this time around you are supposed to have the car serviced (such as a 7500 mile service, 15k, 22.5k, 30k...and so on).

if you only change the oil every 7500 miles, your engine hates you. that is unless you drive the car at least 20 miles, at 65 mph, with no stops, over no hills, and 70 degrees outside...everytime you start the car.