Jupiter Rover said:Doesn't matter where you live. The operating temperature is the same.
You bring up a good point but I suspect all oils undergo similar changes. As for operating temp, it is a range. During the winter engine temp sits just above the thermostat operating point. During the summer it will move up but never 'boil' because 1) the cooling system is operating and 2) the system is under pressure.
I'm much more concerned about low temp performance during a Colorado winter than high temp shear changes. Pour points in the -30's F/C are close to low temps in Colorado. In general I suspect start-up oil starvation is much more of a problem than high temp shear.
It was 24F last night in my area. I know Denver broke the record low last night.