motor oil question

[echo4747]

If you were to mix equal parts of the same brand ( i.e penzoil platinum) lets say: 1 gal of 0w -20 + 1gal of 0w-30 would you have 2 gals of 0w-25?

or equal parts of 0W - 30 and 5W-30 .... would you get 2.5W -30 ?

 

[NutBucket]

No

 

[mindless1]

Yes, mixing oils is not a problem if it still falls within the engine viscosity requirement, except that they round off the numbers to 5's and 10's so the resultant viscosity treated the same way could potentially be rounded up or down too, but you will still end up with a viscosity that's an average of the two if using equal parts of both, or some algebra will calculate it with unequal parts.

It doesn't have to be the same brand.

 

[Jimzz]

Its does not work that way as the number on the bottle is based on a range. So a 10 weight may have a range where one oil is on the "thick" side and one on the "thin" side. So depending on the ranges they use it could be more like a 0w-27 or 0w-23.

But you can mix any oil viscosity, brand, or even type.

 

[deadlyapp]

One thing to note is that mixing different viscosity of oil (generally have different densities as well) you'll get some stratifying of the oil in the oil pan - it doesn't turn into a complete homogeneous blend like you simplify it to. This isn't probably an issue once it starts mixing anyways, but good to note.

 

[mindless1]

^ Motor oils are miscible, do (practically immediately, once the engine has ran to mix it up) become a homogeneous blend. Some additives could settle out over long periods of time (usually only observed at the bottom of an old, "new" jug of oil), but this is as true of a single oil product, is not due to mixing.

The funny thing is so much internet wisdom about not doing it when there is no evidence of a problem doing so, provided the resultant mix falls within the requirements for the engine and climate, which is easy to figure out looking at the API and engine manufacturer specs.

Oil manufacturers state you can mix, but often limit their answer to using their brand because they cannot possibly know what is in every mysterious off-brand oil out there, and like well meaning internet answers, feel it is better to err on the side of caution.

That does make sense in the context of oil not being hard to find and that it is available for any conceivable application, so like anything else in life if someone has to ask about xyz, it's far easier to tell them "Do not do this at home" so nothing could possibly go wrong but that's not really the correct answer.