Changing Engine Oil: How Often Is Too Often?

The Story

Changing your oil every 3,000 miles won.

The why is a little complex, but it has a lot to do with improved oil quality. But even before we study oil itself and why it now lasts longer, there’s a simple tool most late-model cars feature called the the oil life monitoring system. Oh, right, and there’s also the owner’s manual, which will have a table or notation about oil-change intervals, too.

The monitor studies temperature and driving time, as well as total engine revolutions based against an algorithm of oil life. Then it will scream something at you like, “It’s time to change your dang oil!” Older cars may have a symbol you have to look up in the aforementioned manual, or you can always take the car to an auto parts retailer, since most will scan your car’s codes or interpret dash symbols for free. Or, use your own OBD-II scanner to see what any codes mean (depending on your scanner’s capabilities).

The upshot is that ye olde 3,000-mile rule isn’t the best metric for oil change intervals. It won’t gain any added life for your car and is, of course, expensive and wasteful. But this rule isn’t an immutable law. There are times when you should break it.

The organization has set ever-more stringent standards for engine oil, as motors have grown more sophisticated and emissions regulations more focused. ILSAC began in 1992 with engine oil standards focused on conserving energy use. It soon moved on to chemistries that reduced high-temperature deposits, then the long-term effects on the vehicle’s emission system, improved fuel economy, and, along the way, it looked at viscosity performance, oil life itself, and reduced oil consumption, too. As turbocharging took hold, ILSAC focused on both reduced piston and turbocharger wear. Now, over three decades into ILSAC, it’s on its seventh iteration of standards. The newest (called GF-7) was designed to work well with hybrid engines and to confirm that even aging oil is still protecting the engine.

All of that is to say that modern engine oil tech is just better. Engine technology has improved, too, particularly around more accurate control of overheating and warm-up, leading to better combustion. A cleaner burning engine that’s not overheating, with oil that’s not cooking off, doesn’t need oil changes more frequently than 5,000 miles, and some engines can go up to 15,000 miles. Yes, check your owner’s manual. If that feels like too much work, the state of California has a very nifty tool that lets you enter your car model and year to confirm how many miles you can roll before swapping engine juice.

But both manuals — and this will be true for just about whatever you drive — recommend an oil change at least once a year. The reason has to do with oil life generally, not mileage. This comes down to chemistry. Mobil 1’s 25,000-mile warranty says you must change your oil annually, too, regardless of accumulated mileage. Just 1 mile, not even 1,000, may be the right interval if your car’s just sitting in a garage, because oil suffers from oxidation, whether you use it or not, and oil can go bad just sitting in your parked car’s engine.

Oh, and by the way, unlike with that oxidized olive oil in your cupboard, running an engine with oil that’s degraded is bad, not because you don’t want it on your salad, but because it’s thicker. So, now, it’s doing the opposite of what you want — making your engine work harder, not smoother. The simple takeaway is to use that handy link from the state of California to check the actual interval for your car’s oil changes, unless your car lives a grimier existence — or barely ever moves.

Why It Matters

Just 1 mile, not even 1,000, may be the right interval if your car’s just sitting in a garage, because oil suffers from oxidation, whether you use it or not, and oil can go bad just sitting in your parked car’s engine.

CarMotion Daily’s Take

Industry watchers will be following the follow-through, not just the headline.