Is "re-refined" oil okay to use in your car's engine?

Dear Car Talk

Dear Car Talk | Apr 01, 2010

Dear Tom and Ray:

I stopped at a "Quickie Lube"-type joint the other day and asked them what type of oil they use in their least-expensive oil-change service. The answer was "remanufactured oil." I left, because I'd never heard the term before. What is it?

-- Jim

RAY: Oh, that's when they drain the oil out of the Subaru in one bay, and pipe it, through a hose, right into your car.

TOM: Actually, the correct term is "re-refined oil." Technically speaking, it's used oil that has been re-refined, so it can be used again.

RAY: The people who promote re-refined oil claim that the oil itself never wears out; it just gets dirty. And if you clean it, then add back in the additives that got used up, the stuff is as good as new.

TOM: But is it? Well, the American Petroleum Institute says it can be. It depends on how well it's re-refined.

RAY: When it's done correctly, the process is very similar to the way they refine oil from crude in the first place. It involves vacuum distillation to remove dirt, water and used additives, and then hydro-treatments to remove any remaining chemical contaminants. Then a new package of additives, like rust inhibitors, is blended in.

TOM: And if it's tested, and it meets the same requirements that new oil has to meet for qualities like cold-start viscosity, engine wear and rust protection, it earns the API seal of approval.

RAY: So the proper question for the "Pokey Lube" people is not "Do you use re-refined oil?" It's "Is your re-refined oil API certified?" If it is, and if it meets the API service classification for your car (currently SM for gasoline engines), you can use it, and you might even save yourself a few bucks.

TOM: Or you might not. Some re-refined oil is actually more expensive than virgin oil. Just like my recycled canvas-hemp hybrid potato-sack underwear is more expensive than my Fruit of the Looms.

RAY: Re-refined oil proponents, which include the state of California, point out that there are benefits beyond cost. There are environmental benefits of reusing engine oil. It's a way to make use of something that otherwise would be hazardous waste. And it takes less energy to re-refine oil than it does to pump it out of the ground and refine it. We can't argue with that.

TOM: They also say that major manufacturers, including Ford and GM, approve of using re-refined oil in their cars, as long as it meets the API requirements for those cars.

RAY: So it sounds like it's something we're going to see more of, Jim. But since re-refining is such a broad term, it's particularly important to check for proper API certification. Otherwise, you could end up with the four quarts of crud that dripped out of my brother's Fiat overnight.

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