To avoid controversy I recommend following the manufacturers recommendation.
But if anybody wants to know what I actually use it is mobile one 15-50, on the theory that an air cooled engine running continuously at high power settings in hot weather will have much higher piston, piston ring and cylinder wall temperatures than a water cooled car engine running 5 to 25% power settings most of the time.
I have not had to rebuild an engine since following this strategy.
I have an eu 2000 which will run the ac and a sportsman 1000 for cool weather trips. I have a polyethylene squeeze bottle marked for the correct amount of oil for each, which makes changes quick and easy.
Since they have no oil filter I change it frequently, disposing of the old slightly used oil in the car or motorhome which both have high quality full flow filters. I drain it immediately after a long run, before particulates can settle out.