Even at 40C
Originally Posted By: Hermann
Originally Posted By: 901Memphis
Plenty of 10w30 synthetics hit 6-7% NOACK. It's easier to hit lower NOACK compared to a 5w30, but a 5w30 is almost always superior imho.
How?
Even at 40C (104F) a 5w30 synthetic has a viscosity of 55.8 - 65.2 cSt which is thicker than even an SAE 60 motor oil at 100C, far too thick to provide adequate protection to the entire engine under demanding load. An SAE 60 will be between 21.9 and 26.1 cSt at 100C and thats far better flowing than even a 5w30 synthetic in the summer Florida heat when you first turn the key.
If your engine sees cold starts, then the 5w30 synthetic is Superior to 10w30 if the engine specs either. A cold start is a cold start whether its winter in Wyoming or Summer in Arizona.
If you only warm up your engine 1 time per OCI and drive the car forever at 100C across the country then a 10w30 is superior since you won't see as much cold star wear.
Whether or not the amount of wear is measurable is another question, but better flow is better flow and i will not pay the same amount for a 10w30 synthetic when the 5w30 is right there on the shelf unless its going in a lawnmower.
Now if i find some 10w30 PU on clearance at a ridiculous price you better believe i would use it in the summer in a 5w30 application, but i won't go out of my way to buy it.