Oil changes, and how often a car really needs one

For years the advice was to change the oil every 3,000 miles or three months. Better engines and better oil have made that rule out of date. The interval that applies to your car is the one in the owner's manual.

How often

Many automakers set oil change intervals of 7,500 or even 10,000 miles, and six or 12 months. Many cars also have a built-in service reminder that signals when a change is due, based on how the car is used. The manual may give a shorter interval for severe duty. If you drive fewer miles a year than the interval, still have the oil changed twice a year.

The right oil

The manual also gives the oil grade, such as 5W-30. Using the recommended grade can improve gas mileage by 1 to 2 percent. Putting 10W-30 in an engine designed for 5W-30, for example, can lower mileage by about that much, and 5W-30 in an engine designed for 5W-20 can lower it by 1 to 1.5 percent. Look for "Energy Conserving" in the API symbol on the bottle, which means the oil has additives that reduce friction.

Keeping the record

Keep the receipt from every oil change, with the date and the mileage. Service records show the car has been maintained, which a buyer may ask to see. If you have a service contract, it may require you to follow the maker's schedule for routine maintenance like oil changes.

Used oil

The used oil from one oil change can contaminate a million gallons of fresh water. Used oil doesn't dissolve, it lasts, and it can carry toxic chemicals and heavy metals. If you change your own oil, collect it in a leak-proof container without spilling it, and drop it off at a collection center or a shop that takes it. Drain the old filter and take it along too.

An annotated example

What to do next

Find the oil change interval and the oil grade in your owner's manual, and write both into the car's records. After each change, add the date and the mileage and keep the receipt.