Motor Oil Age Doesn’t Matter as Much as Mileage: Study

When it comes to caring for cars we cherish, it's better to play it safe than sorry. If you're like me, you've been changing your oil every six months whether you've done 900 miles or 5,000, wondering if you were premature when it doesn't come out inky black. Well, those days are over for me, because oil analysts at Blackstone Laboratories have tested old oil from a variety of sources, and they say it's the miles that matter most.

The results of several tests were outlined on an episode of the company's podcast Slick Talk: Powered by Blackstone Laboratories. The episode in question was uploaded in December, but only recently gained traction on social media such as Reddit. In it, host Joe Adams recounts pulling a half-full bottle of Mobil 1 0W40 off the shelf, and contacting its producer to find out more about it. The bottle turned out to be almost 14 years old, and Mobil 1 said its age meant it'd broken down and wouldn't properly protect an engine. But when pressed, it wouldn't explain how, so Blackstone ran it through a battery of tests.

Blackstone said it tested a variety of the oil's characteristics, from measuring additives to water content, flash point, viscosity, insolubles present, and the oil's ability to neutralize potentially harmful acids and bases. Even though the oil was made in September 2010 and had been sitting half-full for an unknown period, it tested just fine. That led to several follow-up tests of other old oils from varying sources to work out the circumstances that cause oil breakdown—and the answer was pretty clear.