Regular oil evaporates? While I'm sure this probably is true, I've never had this issue with Mobil 1 in any of my engines.
I fill my lawmower with fresh gas as much as possible, right into the filler neck, put the cap on it and drain the carb and it fires up every spring. My generator I drain the tank, lines and carb, same thing, fires right up.
Snowblower I treat like the lawn mower.
On small engines I also turn the engine until both valves are closed.
I don't own a single bottle of MMO and all of our gas has ethanol. Our 1992 Coleman generator which has somehow survived without MMO.
https://youtu.be/m-QjnoJLgKY