Mixing oil grades?

[Andy Tims]

Sorry if covered before.

My 2020 620S has 5w 50 oil.

The manual also gives 10w 60 as an option. I have some of that so is there any reason not to use that either as top up, or when I next change the oil?

[Amos91]

When you next change oil that is fine, but I'd avoid mixing grades unless it's an emergency. 

[Neil220]

#2

"When you next change oil that is fine, but I'd avoid mixing grades unless it's an emergency"

Why?

[ScottR400D]

No real reason not to mix grades as long as both oils are of suitable spec. 

[eric]

Why do that ???  

 

If you mix  1/3 of Motul 300V  5W50  with 1/3 of Motul  300V 10w40   with 1/3 of Motul 300v 15w50  with 1/3 of Motul 20w60 , you will obtain a Marcel Pagnol Pastis recipe ... not sure it is nice for the engine 

If your question is how to obtain a 10w60 oil with a 5w50 already in the engine ... the answer is : drain the old oil 

[BenF]

Why would that be bad for the engine?  As long as the resulting oil has a suitable viscosity to retain the correct pressure profile within the bearings (from a tribology point of view) I can's see that being a problem.

If you mix two oils, both of which are suitable for the engine, then I don't see any problem with this.  When you drain the oil and change to a different grade, there is always going to be 100-200ml of the old grade left in the engine somewhere and nobody worries about that.

[ScottR400D]

"If you mix  1/3 of Motul 300V  5W50  with 1/3 of Motul  300V 10w40   with 1/3 of Motul 300v 15w50  with 1/3 of Motul 20w60 , you will obtain a Marcel Pagnol Pastis recipe ... not sure it is nice for the engine" 

Well, no, you wouldn't but where has that even remotely been suggested?

"If your question is how to obtain a 10w60 oil with a 5w50 already in the engine ... the answer is : drain the old oil"

it wasn't his question, was it?

 

[jbcollier]

First things first, ANY oil is better than nothing.  But, low spec oils are a poor choice for a high spec engine.  They will not properly protect your engine under stress.  Still, they are fine as a limp home solution.  If oils meet the engine's requirements, then you can mix two different viscosities.  It is not good practice but oil companies do make oils of similar specification compatible with one another.