Fact or fiction: One should never mix motor oils?

Dear Car Talk

Dear Car Talk | May 01, 1995

Dear Tom and Ray:

I have tried to maintain my own cars for about 35 years. Now about all I can do is change the oil, and I'm even having second thoughts about that! One of the first things I was told was NEVER to mix different brands of oil, either between oil changes or at an oil change. Was this some kind of "old wives tale," or is there some degree of truth to it? Should I continue with the training I received in the 1950s, or is it OK to mix brands of oil?

TOM: Well, I wouldn't mix Valvoline with Felippo Berrio Extra Virgin Olive Oil. But other than that, you can mix together any oils you want, Joe.

RAY: There's no TECHNICAL reason to stick to one brand of motor oil. Interestingly, Quaker State is trying to give people a MARKETING reason to use only their oil by offering a 10 year/250,000 mile engine warranty. They say if you use Quaker State exclusively, and change your oil every four months or 4,000 miles, they will replace any lubricated part of the engine that fails.

TOM: Of course, you have to save your receipts, the receipts have to specifically identify the car, you have to file twice a year with the Securities and Exchange Commission and "cc" the National Organization for Women. And then, if something does break, you have to forage through the finest, fine-print Quaker State's lawyers could finagle.

RAY: But if you're well organized and plan to keep your car forever, Quaker State's offer might be worth considering. They'll send you a copy of the complete warranty if you call them at 1-800-237-8645. Have your 10X reading glasses handy, the print is small.

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