Originally Posted By: car51
69GTX: I was in the Wal Mart I walk to and there were 2 jugs of the older M1 0w40 so I got both then submitted the receipt for the rebate. I'll mix with some M1 5w20 EP or.....
This is something I probably wouldn't want to do. The formulations between the 5w-20 M1 and the 0w-40 are quite different. They might as well be different brands. One is very high calcium, no sodium while the other is low calcium, high sodium. You'd end up with a M1 product unlike anything they produce or test.
Based on the latest Castrol 0w-40 VOA, mixing M1 5w-20 and Castrol 0w-40 would result in a more consistent mix (ie both are lower calcium, higher magnesium oils).