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Is it OK to mix oil from different manufacturers during oil changes?

dud

dud

Diamond Member
A friend asked me this question and I didn't know how to answer. When doing an oil change you usually buy N quarts of oil from the same source (Quater State, Valvoline, etc.). His situation is this: My friend is changing the oil in two cars and already has a few quarts of companyX brand. He goes to the auto parts store and buys 5 quarts of company Y's oil. He has enough to do both cars but one change will require him to mix companyX and Y's oil together. Assume conventional oil, both are the same viscocity (say 5-W30) and both are API rated.

I told him that all things being held equal ... it should be fine.

Any input would be helpful. Thanks ...
 
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I did it in my old nissan all the time. Lasted 150K or somewhere close and the engine was still going when I traded it in.
 
It is fine but if the car normally needs a little oil before the next scheduled change I usually purchase an extra quart and shelf it until I need to add a little.
 
Absolutely not. There is no standard among oil manufacturers when it comes to viscosity ratings (Amsoil's 10w40 is nowhere near the viscosity of Pennzoil's 10w40 for example), and if the molecular chains aren't in alignment, you'll get shearing and oil breakdown. Think of it this way, It would be like a chainsaw cutting right through your engine when you have molecular shearing, and your pistons will be unlubed and your crank bearings will overheat and transfer metal. Not a pretty sight.

I can sell you some perfectly aligned oil though if you are interested, only $12.00/qt plus shipping.
 
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