I've never worried about filling the tank up, just put some stabil in there. With the way gas is produced these days with the ethanol and winter blends it breaks down a lot faster than it used to. The stabil will hurt your fuel mileage though in the spring. Both times I've put stabil in it I get about 80 miles to the tank until I re-fill it in the spring. And then it goes back to normal. Scared me at first. I've never bothered with the battery either just once a month if it's above freezing I'll start it and let it run for a few minutes.