How often should you change your engine oil?

Old oil loses lubrication and can seize an engine.

Degraded oil stops carrying heat away and stops holding contaminants in suspension, so deposits form. On turbocharged engines deposits can build in the turbo bearing, and on engines with variable valve timing they can block oil control passages. Both are expensive, and both start as a skipped service.

1. Warm the engine briefly, then stop it. Warm oil drains more completely than cold oil. A few minutes is enough, and it avoids scalding.
2. Raise and support the car properly. Axle stands or ramps. Never work under a car held up by a jack alone.
3. Drain from the sump plug. Position the pan, remove the plug, and let it drain fully. Replace the crush washer rather than reusing it.
4. Change the filter. Cartridge or spin-on. Smear clean oil on the new seal, and tighten as the filter maker instructs, which for most spin-on filters means by hand.
5. Refit the plug to torque. Use a torque wrench. A stripped sump thread turns a cheap service into a new sump.
6. Refill with the correct specification. Match the manufacturer’s viscosity and specification, not just the grade. Modern engines are specific about this.
7. Check level, run, then recheck. Fill slightly short, run for a minute, let it settle, then top to the mark. Check underneath for leaks.
8. Reset the service indicator. And take the old oil and the drained filter to a recycling point. Never pour oil away: the US Environmental Protection Agency says the used oil from one oil change can contaminate a million gallons of fresh water.

• The service light or oil life monitor reaching zero
• Oil on the dipstick that is black and thin rather than amber and viscous
• A ticking or rattling on cold start that fades as pressure builds
• Oil level below the minimum mark, which is a separate and more urgent problem

• Using the wrong specification oil because the viscosity matched: engines with particulate filters often specify a low-ash oil, so check the handbook rather than the grade alone
• Reusing the sump plug washer, which can leave a slow weep afterwards
• Over-tightening the filter, which distorts the seal
• Following a long mileage interval while doing mostly short trips, which AAA lists among the severe conditions that call for more frequent changes

• AAA counts trips of 5 miles or less, sustained stop-and-go driving, heavy loads or towing, and extremely hot, cold or dusty climates as severe conditions
• Full synthetic oil generally runs longer between changes than conventional oil
• Time matters as well as distance: AAA advises changing the oil once a year even if you have not covered the mileage

If oil pressure warning lights come on, stop the engine immediately and do not restart it. That is not a service interval question.