different question about oil visc. mixing

[Steve S]

Are oil molecules for a given viscosity about the same size? If so then the molecules are a different size for 30 wt. as compared to 50 wt? So if we mix 4 qts of 30 wt with 1 qt of 50 wt the average viscosity would average to a 35 wt. but would there be difference in the cushioning effect because of the 50 wt molecules due to their larger size ?

 

[TallPaul]

Here is a LINK that may help.

My understanding is that the most oils are formulated with a mix of several viscosities of base oil, and so you already have variable molecule sizes. So mixing should not be all that bad if the two oils are not that far apart, say SAE 30 and SAE 40, but I suspect a mix of 10w and SAE 50 would not be the best performer.