Gasoline eventually goes bad and fouls the engine. Best thing is to top off the tank as much as possible, otherwise moisture in the tank will foul the mix. Because of ethanol in the gasoline, the water content in ethanol will separate and contribute to fouling the tank. Another best practice is to constantly refresh the gasoline, don't let it sit for months. I have owned vintage cars, and have had to deal with tanks that went bad - gasoline turned to a gummy stinky mess after sitting for some years. Have had to boil out the mess by dipping in acid tanks. Use up your gas quickly and preserve your car.
Thanks.
My driving is limited, perhaps 100 miles/month. I suppose I should look for an additive of some sort?