Oil Change Time vs Mileage: When Should You Change Your Oil?

When you get your oil change performed, it’s fresh and clean inside the crankcase. Usually, a new filter has been installed. And now you’re good until the next time, but when should that be? For decades, oil changes were scheduled every 3,000 miles or 3 months, but that’s not a very common interval anymore as higher-grade oils are used, and engines are built more efficiently.

And with the improvements in part quality and the increase in labor costs, oil changes have become more expensive too. Rather than the common $20 corner shop oil and filter change from years gone by, most drivers can expect to pay around $50 and up for the service today.

When is it best to change your engine oil, and how should you determine the interval? Here’s what you should know.

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When should you change your oil?

Ideally, you should change your engine oil when the condition begins to deteriorate and can’t protect your engine as well as it used to. You should be able to check your oil to determine:

  • How much is remaining in the crankcase
  • If the oil is contaminated by water, making it look like chocolate milk
  • If the oil is breaking down or laden with gritty carbon particles

Sometimes, the condition still looks good after several months of use, but it’s still due to be changed. The criteria used to set oil change intervals has changed with more adoption of synthetic and synthetic-blend oils. So, if the condition is fine, the owner’s manual is the best place to check for the correct oil change interval for your specific year, make, model, and engine size.

And what about the oil filter? It captures and stores many of the contaminants that could otherwise wear or damage internal components. For the best protection, it’s highly recommended to replace the engine oil filter during every oil change service. But at the very least, replace the oil filter on every other oil change.

Time based service

Depending on the vehicle, the service interval will have a time-based component. On older vehicles, the interval may state that the oil should be changed every three months, six months, or once per year. If that’s the case, you should not exceed that time frame.

Time-based services are established because natural degradation occurs in engine oil, and it’s accelerated once exposed to moisture and other contaminants. If you drive your car for only 100 miles with fresh, clean oil in the engine, it will still degrade and oxidize and, eventually, it won’t protect the engine like it should.

Mileage based service

Likewise, on most vehicles, there’s a limit to how many miles you can drive before the oil needs to be changed. The average distance used to be 3,000 miles before an oil change was required, but for most modern vehicles, it’s 5,000 miles or more. You should have the oil changed before you reach that mileage limitation.

When engine oil is used, it thickens from exposure to high temperatures and the additives intended to clean and protect inside the engine break down. Some of the oil dissipates as vapor or is consumed by the engine, and the oil level becomes low. Contaminants become suspended in the oil, causing it to look darker Continuing to drive when the oil is dirty or low can create wear inside the engine as well as higher heat than normal and other issues.

Oil life monitor

Rather than an oil change mileage or time interval, there’s another option. For a majority of vehicles made in the last few years, an oil life monitoring system tracks your usage and predicts when the next service is due. It combines factors including operating conditions, time, and mileage to estimate the best time to change the oil prior to experiencing issues related to poor oil quality.

Oil life monitors, or OLMs, could predict your next oil change in as few miles as 3,000 or at more than 12,000 miles, all relative to how your vehicle is used. It shows up on your dashboard as an oil life percentage, and your service should be performed before it reaches 0% life remaining.

Which is better?

If your vehicle has an oil life monitoring system, that’s almost always the best way to track when you’re due. The exception is when you use your vehicle in ways outside of normal operating conditions, like off-roading and towing heavy loads frequently.

If your vehicle isn’t equipped with an OLM or you’ve chosen not to use it, how to you pick between oil change time vs mileage?

You don’t. An oil change interval gives you two specifications: time AND mileage. On an oil change window sticker or on your instrument cluster’s service reminder, you’ll find the next service is stated as something like “3 months or 5,000 miles”. That means you need to take both figures into consideration. It would be best thought of as “3 months or 5,000 miles, whichever is sooner”.

Regardless of how you track your oil changes, it’s vital that you have a new engine oil and oil filter installed at least once per year.

Is it time for an oil change? Get your motor oil at AutoZone from popular brands like Valvoline, Mobil 1, Castrol, and others. Need help finding your service interval? An in-store associate can assist you with service information and other crucial information on maintenance and repairs.

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FAQ/People Also Ask 

Does time really matter for oil change

Yes, time matters! Oil begins to oxidize and degrade as soon as the container is open and it’s exposed to the operating conditions inside the engine.

Is it OK to drive past the oil change mileage?

Oil change intervals are set to keep your vehicle operating at its best, and going past the mileage could mean you’re risking harm to your engine.

Is it OK to change oil once a year?

It depends. For vehicles that accumulate very few miles and use high-quality synthetic or semi-synthetic oil, once per year might be enough.

Is oil life based on mileage?

Oil life considers mileage since your last service, yes. However, it also factors in the operating environment, mileage, and other conditions to estimate your next service.

Should I change oil every 6 months?

Many carmakers have switched intervals in recent years, and six months is a relatively common time frame for an oil change. Refer to your maintenance guide for the right interval for your vehicle.

How often to change oil if you don’t drive much?

If you won’t hit the mileage interval for an oil change, consider using a premium oil product and performing an oil change once per year, as long as it’s permitted in your maintenance schedule.

Advice, how-to guides, and car care information featured on and AutoZone Advice & How-To’s are presented as helpful resources for general maintenance and automotive repairs from a general perspective only and should be used at your own risk. Information is accurate and true to the best of AutoZone’s knowledge, however, there may be omissions, errors or mistakes.

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