How Often Should You Really Change That Engine Oil?

You've heard that old advice countless times: “You should change your oil every three months, or 3,000 miles." While commonly followed, is this rule still true today? How often should you really change your oil? Let's take a look at the specifics of oil changes.

Check oil with dipstick

Why Change the Oil?

If you're the DIY type who changes your own oil, you probably return the used oil back to the retailer for recycling. But that brings up a good question: if it can be recycled and used again, why even change it at all? It's not that the oil goes bad, but the oil in your engine becomes contaminated and loses efficiency. You want clean oil lubricating your engine, not contaminants and grit.

The slight clearance between moving parts—say, between piston rings and cylinder walls—allows trace amounts of burned fuel to mix with the oil, contaminating it. Over time, these contaminants will turn your oil dark. The oil filter keeps a lot of that junk from circulating in your engine, but it has a limited capacity. When the filter can no longer keep the contaminants out of your oil, it's time for an oil change. If you go too long without one, the contaminants build up and can cause costly sludge issues.

How Many Miles?

The 3,000-mile oil change guideline has likely been around longer than your parents have been driving. Many drivers still stand by it today. There are a lot of arguments here, as many of us have been rewarded with a reliable vehicle after religiously changing the oil at 3,000 miles.

Studies, however, show that might be a placebo effect. While a $50 oil and filter change is cheap preventative maintenance on a $30,000 vehicle, everyone from Edmunds to the New York Times agrees that the 3,000-mile oil change is no longer applicable in today's vehicles. The rules have changed with the tech of the last 50 years. With the innovations in tighter build tolerances and higher-quality synthetic oils, many sources suggest a 5,000-mile to 10,000-mile oil change should be the new normal.

 Check Your Manual

Some of the discussion over proper oil-change intervals may come from your owner's manual. Most manuals list two different recommended mileages for oil changes based on whether your driving routine is “normal" or “severe." Normal driving is considered the usual daily commute. The more frequent "severe" service schedule should be followed for commercial vehicles, or when using your daily driver for towing, off-roading, or racing.

Even a single manufacturer can have different mileage recommendations based on the engine type and recommended motor oil. For example, Toyota uses 5W-20 in the Rav4, and recommends changing the oil every 5,000 miles. On the other hand, Toyota also recommends lighter 0W-20 in the new Prius, which it says is good for 10,000 miles (if you periodically monitor the oil level). Then there's the Tundra, which needs a 2,500-mile service when using E-85 fuel. For peace of mind, read the manual.

When in Doubt, Send It Out

If you want to geek out over this and know exactly when to change your oil, science can help you out there. Blackstone Labs is one service that analyzes the chemical makeup of used oil, and can offer fascinating insight into what is happening with your oil, and your engine, as the miles add up. If the analysis shows unusual engine wear, there are additives that can resolve the issue, giving you many more years of problem-free driving.

While the recommended oil-change interval has increased over the years, one thing that remains constant is the need to change your oil.

Do you stick with 3,000 miles or follow the manual? Tell us in the comments.

Last updated June 12, 2017

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