Here's Scientific Proof You Should Never Use Old Oil

That oil that's been sitting on the shelf for the past decade? You might as well throw it out.

Photo by: YouTube

By: Brian Silvestro

Aug 11, 2024 at 12:00pm ET

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You might want to think twice before putting that old can of oil in your car. According to this study put on by The Motor Oil Geek on YouTube, expired engine oil is downright dangerous for your engine.

Host Lake Speed Jr. set out in this video to show whether old oil, when shaken, could be brought back to a usable state. He dug out a couple of old sealed oil containers—one in a plastic container and another in a metal can—to see whether a good shake could bring them back to life.

The lab results aren't surprising. Whether we're talking about the 20-year-old Valvoline oil or the 50-year-old Mobil1, both showed significant signs of oxidation, shaken or not. Essentially, that means the oil itself, as well as the set of additives put into the oil when it was new—Zinc, Phosphorus, Sulfer, etc.—have chemically degraded to the point where they can no longer lubricate an engine sufficiently.

The plastic bottle of Valvoline was the worst of the two. It showed signs of water present in the oil, gathered over the course of two decades simply through the heating and cooling of the container. So we advise against using that old bottle of oil in your garage, even if it's for a top-off.

Parts suppliers like Autozone and CarParts.com say most motor oils have a shelf life of about five years. After that, oxidation begins to occur, degrading the quality of the lubricant. If you think your oil might be on the fence, Speed Jr. made another video showing how you can check the health of your oil at home, without the use of fancy testing machines.