I know the logic of sticking with the same oil year round in vehicles; and I know you can use 10W-30 in yard machines, pressure washers, that kinda thing. Backup generators have engines like that; they're just 8HP or some such.
The part that throws me off is, they run wide open for hours and many have an 'hours run' meter, or whatever it's called; and the recommendation is to change the oil/filter after so many hours of full operation. Dad was good at winterizing/storing things like generators, that sit unused for long periods, so, I'm sure the generator's okay. I'd just like to see for myself before I have to wind it up. I'll prob'ly do this A LOT; but as Dad used to say, 'It's one of those 'roundtoit's.' 'I'll do it when I get 'rountoit.'
Gas gensets don't really run balls out. Though it may seem like it, they don't. Kind of like your lawn mower. They are designed to run at one speed without ill effects (as long as you maintain it).
They have an hour meter, because they don't have an odometer. It's the same concept. Run for a certain amount of time and change the oil/filters.
As for winterizing, or long term storage....Dump a can of Seafoam in the gas tank (can be found at any auto parts store, and IMO, the best fuel stabilizer/carbon cleaner out there). Start the generator, close the fuel valve, and run it until it shuts off. The fuel bowl in the carb will run dry, eliminating the ethanol from fouling the carb up. The Seafoam will keep the fuel stable for awhile, and when you go to fire it up again, it will clean the carbon from the valves and combustion chamber.
We are, of course, talking about small, home generators. Getting into diesel backup power gensets, and we have to talk about loading the generator at least 30% to prevent wet stacking, but I digress.