M1 HM 10W30 vs. M1 0W40

Messages
53
Location
Cincinnati, OH
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??
 
Messages
336
Location
Texas
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
 
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