Can mixing oils dilute 'cold start' properties

[pbm]

I used to mix oils a lot due to having leftover quarts from a case of 6 or 12. Since finding this site and reading a lot I am less likely to mix and more careful when I do.

Sometimes I have odd quarts and will mix the same brand.

Is it possible that mixing even the same brand could have negative affects as far as throwing off the balance...For instance if I were to mix 2 quarts of Mobil 1 0w30 with 3 quarts of Mobil 1 5w30 I would assume that it would have slightly better cold properties than all 5w30..am I correct? Could the differences in the formulation have a negative effect? Thanks

 

[A_Harman]

There was a thread here a few months back that discussed the effect of mixing on cold flow properties. There were a couple of papers referenced that said even mixing different viscosities of the same oil brand causes unpredictable changes in cold flow properties. Another point was made saying that old oil has worse cold flow than new oil, so it is beneficial to change oil right before the cold weather comes.

So what did I do for my winter oil change? Mixed 3 different viscosities of Redline!

 

[A_Harman]

Here is a link to the previous discussion:

https://bobistheoilguy.com/forums/posts/2374150/

 

[Drew99GT]

Part of the GF-4 and GF-5 performance upgrades was to help maintain cold flow properties over the life of an oil change interval.

 

[CATERHAM]

Originally Posted By: A_Harman

So what did I do for my winter oil change? Mixed 3 different viscosities of Redline!

Except RL actually encourages the blending of their oils to achieve whatever optimum viscosity or other attribute that you want.

With Mobil all their oils are mixable with predictable results.
I recently asked them about various blends and the effect on MRV; specifically Mobil 1 0W-20, Mobil Delvac Elite 222 0w30 and Mobil 1 0W-40. They could not tell me precisely without actually testing but the result would not likely be an average of the MRV spec's but would be on the heavier side.
So mixing Mobil 1 0w30 and 5w30 will give you a 5w30 with a lower MRV. At the less extreme temp's of NY, there is very little difference between the two oils anyway so any blend will result nothing noticeable.

 

[pbm]

A_Harmon

That old thread is very informative.
On the other hand I'm leaving the Mobil 1 (0w30-5w30) mix in my Corolla unless I feel it struggling when the weather gets real cold.
Thanks