The 3,000-mile oil change is dead. Cars can be driven more miles between oil changes than this outdated rule of thumb would have you think. Which leads to a slippery question: How often should you change your oil?
You could just ask your mechanic. However, that’s an invitation to recommend too frequent oil changes. It’s a mistake to “drop the keys on the counter and tell the mechanic, ‘Do what you think is right,’” says Richard Reina, product training director at auto parts site CARiD.com.
Instead, arm yourself with knowledge about what your car needs. You’ll save time and money — and protect yourself from upselling when you take your car in.
How often to change your oil
There are two ways to know when it's time for an oil change:
1. Look in your owner's manual. In the scheduled maintenance section, the manual tells you how many miles or how much time you can allow between oil changes. Most manufacturers also recommend changing the oil filter — an inexpensive item — when you change the oil.
Many owner's manuals list oil change schedules for severe and normal driving. If your driving habits fit the description of severe, such as driving at low speeds, extensive idling or towing a trailer, you’ll need more frequent oil changes.
For example, the manual for the 2016 Mazda3, a popular compact car, recommends oil changes every 7,500 miles, or six months, for normal driving and every 5,000 miles, or four months, for severe driving.
If you’re not in the mood to crack this seemingly impenetrable book, look for it online. Most manufacturers now have online versions that can easily be searched.
2. Look for the service light on your dash. Some cars have a light that says “service” or “service now” while others have an icon of a wrench or some other symbol. Generally, when the light comes on, it’s time to schedule an oil change.
However, the service light might be telling you that you need other maintenance performed, too, such as a tire rotation or routine inspections. To find out exactly what your light means — you guessed it — look in your owner's manual.
Oil life monitoring systems
Some cars use a different system for calculating when you need an oil change, although they, too, display a service light. Sometimes called “oil life monitoring systems,” a computer records information about how you drive, such as how long you drive and the engine’s operating conditions. It then determines when an oil change is needed.
The quality of the oil isn’t measured; instead, a calculation is made based on your driving patterns. So, if you take a lot of short trips, the light might come on after driving only 5,000 miles. If you do a lot of highway driving, which causes less wear on the engine, it might come on after 6,700 miles or more.
If you have an oil life monitoring system, you don’t have to worry whether you are under the normal or severe schedule — the car’s computer figures out what's best. You can find out from your owner’s manual whether your car has an oil life monitoring system.
Why frequent oil changes aren’t actually better
After an oil change, your mechanic might put a little sticker in the corner of your windshield telling you to come back in 3,000 miles. Over 60,000 miles of driving, that would be 20 oil changes, compared to 12 oil changes if you followed your manual's recommended 5,000-mile intervals.
Should you follow the repair shop’s timeline? After all, giving your car an oil change feels like you’re giving a reward to a hardworking friend.
But experts say that too frequent oil changes won’t make your car last longer or run better. Plus, you’re throwing away your time and money and a natural resource.
And while the oil change itself isn’t too expensive — between $42 and $79 for most cars, according to RepairPal.com — you’re likely to get pitches for additional services you might not need.
Changing your oil too frequently, and the dumping of waste motor oil, are also bad for the environment. Though much of it is collected after use, used oil “continues to be a serious environmental problem because it is insoluble and contains heavy metals and toxic chemicals,” according to the California Integrated Waste Management Board.