I guess for an older engine a little extra oil is OK, but remember that nothing like Ultra existed when the old saws were built. The idea that oil displaces fuel does not make sense to me. It may thicken it up so that might cause it to flow slower through the carb, resulting in leaner running unless tuned for. Too much oil and it won't run. A little too much oil and carbon deposits and coking may be a problem. I had a man (engineer!!!) bring back a 2 month old MS 250 that would not run. Pulled the muffler and the piston was black, rings stuck, heavy carbon on top of the piston. He said, "I am an engineer and I do not believe the instruction book is correct. No engine can run on 50:1 oil ratio. So I mixed at 25:1". I think I convinced him once it was apart.
But the fuel does cool the piston. Fuel gets atomized in the carb, or mixed with air, but that is just a pressure equalization thing. Fuel needs to be vaporized to burn, and burn well and completely. And energy is required to vaporize the fuel, since it is changing from a liquid to a gas. When the air-fuel miix moves through the transfer ports into the combustion chamber, the fuel droplets vaporize, and extract heat from mostly the piston and some from the cylinder to do this. Vaporization cooling is what keeps an air cooled two-stroke from overheating. I have put a temp gauge thermocouple under the spark plug, and as the engine is tuned lean the temp goes up. And on a saw, with no rev-limiter, the RPM goes up, and the piston overheats on the ex side, scores and the engine quits.
