M1 HM 10W30 vs. M1 0W40

[shadowvox6]

Group,
Over the weekend, I did some work to my car that for safety's sake, required me to change the oil. I did have M1 high Mileage 10W30 in the car (all WalMart had at the last OC. This weekend, I was at a parts place, and didn't feel like going to Wally World, so I got 5 qts. of M1 0W40. I had ran it in my 99 300M with no ill effects. I put this in my 04 300M Special. I would think the differences wouldn't be that great, other than the cold starting characteristics, and slightly greater protection at warm up.

Any thoughts??

 

[marco246]

I'd be surprised if you or your motor could tell any difference between these two oils. They have the same pour point (-54*C) and at 40*C the kinetic viscosity is 80 cSt for the 0W-40 and 78 for the 10W-30. The HTHS is 3.6 cP for the 0W-40 and 3.66 for the 10W-30. The initial kinetic viscosity at 100*C is what accounts for the 40 and 30 gradings, with 14.3 cSt vs. 11.8. Considering the 0W-40 has been known to shear significantly in many applications, I would think that particular difference in the two oils could dwindle pretty quickly. E.g., in my old V8 Ferrari, M1 0W-40 sheared down to 11.3 from 14.3 cSt in only 1250 miles. I would GUESS that the 10W-30 will be more shear stable, but I have no data.

Since the 10W-30 is a high-mileage oil, I suppose it has some seal conditioners and other additives not found in the 0W-40. My GUESS is these would have little or no effect on your 300M unless it has lots of miles on it. But they couldn't hurt.

Cheers, Mark