
Every vehicle that is on the market has a recommended oil change interval provided by the vehicle's manufacturer. Each vehicle is different. As a general rule, many newer vehicles have an every 5,000 miles or six months oil change interval. Older vehicles often need their oil changed every three months or 3,000 miles.
Even though you don't drive three or five thousand miles in a given period, you still need to change the oil because the manufacturer has provided a time recommendation as well as a mileage recommendation. Oil breaks down over time, so it needs to be changed.