I've found and have verified this in several places, that Stabil floats on top your fuel which creates an air barrier. This keeps the air from reacting with the gas which keeps it from going bad. The rub is if you disturb the vehicle, or the can, you break that film and it can't be reestablished. So really the only true application is for your summertime car which you are going to park and not move over the winter. Not sure if that is going to do anything to save the gas in your fuel bowl though......
On the other hand SF mixes with the gas so no worries about moving vehicles and cans around. I learned this the hard way when I decided to leave my tractor gassed up over the winter with Stabil in it. Every spring the carb was clogged. Decided not worth the headache just so can move firewood around. My wheelbarrow never lets me down!