Hi. New 850 (1993) is near 170,000 miles. Service light recently started coming on. Per maintenance records, last tuneup was a year ago. Last oil change about 6,000 miles ago. I will be bringing this car to mechanics for necessary work, and want to do all the right things to make the car last. With a car this old, what sorts of things need to be done/checked regularly? For instance, right now, w/the service light coming on, a mechanic is saying it needs an oil change. But is that the only reason a service light might come on? Sorry to be so basic, but thanks for any advice.