There was a time when every tech school I attended warned specifically against synthetic oils, and synthetic additives. I disregarded the warnings, and ran Valvoline Syn-Flow, the full synthetic oil in their line up. We had internal cylinder head temp gauges and oil temp guages on a couple select machines. When we ran synthetics, combustion chamber temps dropped 120°and internal oil dropped 15°. We then added an external oil cooler to drop the temps another 35°. We had a couple Kohler 22HP V-twins that dangeled with 5000 plus hours, cylinder heads never removed.
You don't want to run synthetics as break in oil, because it is so slick the rings won't seat. After break in, that is all we run. Call it what you will, the stuff works. Mobil one has made very significant advances in synthetic oil technology. We still run Valvoline, as it is the number one most widely used oil by engine builders from NASCAR, NHRA, CART, ARCA, etc etc.
I found it comical that when the Pennzoil car came to the garage, the crew chief dumped Valvoline into the crankcase.