Time and mileage intervals vary by vehicle manufacturer and whether an engine requires synthetic oil, which is meant to last longer, or regular. Use the guidelines in your owner’s manual, including whether most of your driving qualifies as happening in “severe” conditions, such as frequent short trips and stop-and-go driving. Under those conditions, you should change the oil more frequently.

You should change the oil as often as is recommended by the vehicle manufacturer in your owner’s manual. That’s every 7,500 to 10,000 miles on many vehicles. Many mechanics recommend doing it more often, such as every 5,000 to 6,000 miles or every six months, whichever comes first. If you do mainly short trips or stop-and-go driving, you should change the oil more often. It may extend the life of your engine.

Oil is what makes your engine work. It lubricates and cleans moving parts and performs a vital cooling function as it circulates. Over time and with cold starts, short trips and engine heat, oil gets dirty, becomes thicker and loses its ability to prevent sludge and deposits from forming. Mechanics often say that changing the oil is the best preventive medicine for extending engine life.