The setting on the air cleaner is to aspirate warmed air once the generator is running, it has no beneficial effect on starting it. Wear from cold starting isn’t the concern with these generators – it’s spinning them fast enough to get them to start and remain running; they don’t generate all that much heat when firing up, and there’s a lot of block to put heat into – which keeps cooling the combustion chambers and makes it problematic to start when cold. That is why it’s so critical to have the GPs working properly in all cylinders and the inlet air pre-heater working as well.
Heating the oil just allows the batteries to spin the engine over faster, which allows the heat to build faster in the combustion chambers and the engine to start and run more easily.
One would assume that when using any type of oil pre-heater - whether attached to the pan or a dipstick type – that it would be plugged in all the time to keep the generator warm and ready to start, and you're not just trying to heat it up once you need to start it. If you only try to preheat it when you need it, then you’ll need one of the propane powered solutions to provide enough hot air to warm it up. Trouble is, the colder it gets, the less the propane wants to change from liquid to gas, and the harder it is to make heat effectively. Chances are also good that your generator batteries will also be discharged in the cold, making it harder to start – if you can start it at all.
For me, you can’t beat having a trickle charger on each battery, and if you need to store it somewhere cold use some form of oil pre-heater (dipstick or stick-on pan) that’s plugged in all the time (you had to run the cord out for the charger anyway, so you might as well heat the oil a little),and covering the unit with a tarp to keep the wind from stealing away all the heat you so carefully and expensively put into the block. This presumes that you do try to start it before it cools off once the power fails, however. No single solution solves all issues – so always be as ready as possible.