How Often Should You Change Your Oil Actually?

Let's take a deeper look at one of the oldest and most controversial questions in the automotive kingdom: how often should you change your oil? It's an important question, because oil does a hell of a lot: it lubricates your pistons, bearings, chains, camshafts, cranks, kumquats (just kidding, that last one is a fruit) and is a vital part of your engine's cooling system. You gotta keep it up to snuff. 

When your father and your father's father were growing up, 3,000 miles was the standard oil change interval, no questions asked. Then synthetic oil came into the picture, and some people changed their tune in favor of a 5,000 to 7,500 mile interval. Flash forward to today: some manufacturers in the US recommend 10,000 miles. Abroad, that occasionally climbs as high as 18,000 miles.

None of those are actually right. Because this timeless query has a surprisingly complex answer.

The 3,000 mile interval is an outdated myth

Right about now, your 3,000-mile-oil-change father is going on a rant about what I'm sure he'll call the "insurance" of changing your oil more frequently. It can't hurt to change it more often, he'll say. That's true, but it's a waste of money. Times have changed!

The rise of synthetic oil bases (which, unlike regular, or “dino” oil bases, don’t break down over time), the increase of cleaning and lubricating additives (which do still break down, but do a world of good), better machining tolerances inside engines (meaning less metallic particles grinding their way into the oil), and vastly improved filters to catch any additional particles -- all these combine to extend the life of your oil. By how much? Well, therein lies the controversy.

Theories on the internet are an excellent source of entertainment

People online enjoy debating many wonderful topics, including whether oil intervals should be longer or shorter. You'll see a lot of your dad's folksy "well, it can't hurt" wisdom, and a lot of spurious arguments from complete asshats. Some advise following what the car manual says, no exceptions. But many lovable contrarians think any set recommendation from a manufacturer or a mechanic is made up by Big Oil so you'll spend more money. Almost never are they based on legitimate data.

You can't really trust what your car tells you, either

Some modern cars adhere to what's known as Condition Based Service, which in brief means it uses a combination of sensors and algorithms to predict when the oil needs changing, and it'll give you a heads up when its time to hit a service station. I don't mean to suggest you ignore it entirely -- as a general rule, they do a reasonable job of estimating intervals based on whatever the engineers consider to be an average driver. Oil, however, is very sensitive to your personal driving style and environment. Which brings me to...

Think long and hard about the type of driving you do

Do you start your car in the morning, drive one mile to work, shut it off, restart it at the end of the day, head back home, and repeat the process five times a week? Do you live somewhere where the winter temperatures are so vicious you could throw boiling water out the window and watch it freeze? Do you ever take your car to a race track and have lots and lots of fun? How hard you drive your car, how often, in what kind of temperature, and a ton of other factors might add up to mean you should get more frequent oil changes.

I know, I still haven't answered the question. Well...

The only way to really know? Send your oil off for lab work.

The only way to know for sure is to analyze oil from your car, which has borne the brunt of your driving style. For less than the cost of an oil change, you can send off a sample of your oil to a laboratory that will be able to tell you a) if you can go further between changes, b) the condition the oil is in, and c) the relative health of your engine, and more.

This is the only way you can pinpoint precisely how often you really need to change your oil. The fact that it's also a de-facto early warning system for your engine's health just pushes it into no-brainer territory.

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Aaron Miller is the Cars editor for Thrillist, and can be found on Twitter. For years, he changed his oil every 3,000 miles, even though he's always used fully synthetic.