Should you change your oil every 15,000 miles? Here's how to decide

There is good news and bad news when it comes to the 15,000 mile oil change — a standard five times longer than those often recommended by the quick-lube merchants. The good news:  Yes, it is possible with certain vehicles and motor oils, to do so with no harm to your car.

The bad? Unless you plan on keeping that car until half-past forever, you likely won't see any long-term benefit from doing it.

Most automobile engines are now designed to last well over 250,000 miles with proper care and conventional motor oil.  To make matters better for owners, a lot of these motor oils now come with additives that can better resist the depletion and breakdown process. This resistance helps the motor oil maintain the viscosity needed to keep your engine running properly, and helps prolong oil change intervals to a moderate degree.

A few vehicles require the more-expensive synthetic oil, a recommendation that used to be the sole domain of higher-end vehicles such as Maseratis and Ferraris (and, surprisingly, the Chevrolet Corvette). Today, even entry-level vehicles such as the Mazda 2 and Ford Fiesta now demand full synthetics.

Due to better quality chemical additives, conventional oils are lasting longer than ever with many manufacturers now promoting 7,500 mile to 10,000 mile oil changes under certain driving conditions.

So why would you want to go 15,000 miles with a full synthetic oil that can often cost more than two to three times as much as conventional oil? There are three potential reasons: You want to baby your car, you prefer to do oil changes yourself to save money or you expect the car to take a significant amount of abuse.

For most, the decision may be as simple as using a better product at a lower, long-term cost. Yet there can often be confusion between what the manufacturer recommends in the owner's manual and what your friendly mechanic/lube consultant says.

To help decide if a 15,000 mile oil change works for your car, answer these six questions:
Question 1: Do you just want to use conventional oil and follow the oil change requirements in your owner's manual?

Yes: Do that. Your engine will probably outlast your interest in the car.
No: Next question. Think hard on this one.

Question 2: Is your engine still covered under a warranty... and do you value that warranty?

Yes: Just follow the oil change requirements in your owner's manual, and save the records. Should anything happen to the engine, the extra hassle of defending your choices won't be worth it.
No: Next question.

Question 3: Are you willing to get your oil analyzed for $25 by a laboratory that helps determine your oil's wear levels and contaminants?

Yes: Get an oil analysis done. This can give you insights into just how well your engine is running.
No: Stick to the owner's manual.

Question 4: Did your oil analysis state you can have longer oil change intervals?

Yes: Bingo. Use a synthetic motor oil and an oil filter that guarantees a 15,000-mile oil change interval. But there's one more step.
No: Just follow the oil change requirements in your owner's manual.

Question 5:  Are you willing to drive this car up to the longer oil change interval with the synthetic fluid and filter?

Yes: Do that and then get the synthetic oil analyzed — to make sure that the 15,000-mile run worked properly.
No: Keep the conventional oil and enjoy the longer oil change interval. Make sure you top off the oil periodically during the extended period since this helps replenish additives and keeps the oil at the right level.

Question 6: Does the second oil analysis state that this synthetic fluid will easily last 15,000 miles?
Yes: Congrats! Again, make sure to top off your oil level every 1,000 miles since that adds to the overall quality of your motor oil.
No: If you just want to use conventional oil instead, revert back to the findings in your first oil change analysis.

Not everyone is better off with a synthetic oil. In fact, I use a conventional oil with a 9,000 mile oil change interval for a 2002 Toyota Prius that now has 206,000 miles. That engine was characterized as a "spring chicken' by the laboratory that tested the metal contaminants in my motor oil, and I do my best to maintain it like a top.

With that said most cars on today's roads can still hit the highest mileage levels with a high quality conventional oil and a caring owner. So if you do go down this route of fewer oil changes, make sure you have the right habits when it comes to caring for your car.

Photo: Robert Couse-Baker via Flickr