But under what kind of operating conditions? I'm not going to argue the fact that oils with a higher HTHS will protect an engine better under harsher conditions (high oil temps, full throttle) but I still maintain my strong belief that for the average person with a non high performance engine like this Corolla in most of the US and Canada's climate, the HTHS of a 0w20 will protect that engine more than enough to get it well past 300,000 miles, and quite likely even further than that.
That being said, for my Corvette, I chose right from the beginning to stray a little bit from the norm, with most people going with the regular M1 5w30 with an HTHS of around 3.1, I instead decided to go with M1 ESP 5w30, with it's higher 3.5 HTHS. I did this for a few reasons, one is because I know that when driven hard this LT1 engine can heat up it's oil (230-240F after a little bit of spirited driving) and also because I do oil changes according to the OLM, so I'm usually at around 7500 miles. I know that's not a lot, but in previous Corvettes that I've had, regular M1 5w30 was thinning out a little bit on my UOAs with those kind of intervals. The ESP 5w30 has proven itself in my UOAs to be rock solid in it's viscosity on those slightly longer than typical interval (for a Corvette owner anyway) Even though I don't beat the Corvette super hard every time I drive it, there are some days when I like to push it harder (like yesterday when I took it out for a rare December drive and had some fun with it on the highway for an extended period)
So in a nutshell I'm not disagreeing with the fact that higher HTHS can reduce engine wear in some applications, I'm basically saying that the HTHS of a 0w20 is more than enough to get a solid engine like the one in this Corolla to a very high mileage.