I run 10W40 or 20W40 during the summer in the AZ desert. Full synthetic of course. I prefer Valvoline and normally use 10W30 during the cooler months.
Interesting. Climate here is not as extreme as AZ summers, but just went from 5x30 to 10w30 due to mileage over 100k in one vehicle. Using Mobil semi synthetic. I never go over 3500 for oil changes, and I always keep it near the top mark on the stick. The more oil the more heat dispersion.
Also when I change oil/filer I let it drain for 3 hours. Unlike the local jackball lube places. They always leave about a a 1/4 quart of dirty oil in the engine. At start up I fill the filter half full of oil then screw it on so the motor has oil where it’s needed fast at start up.