Does gasoline lost its volatility if it just sits around? Reason I ask is

[ProfessorGAC]

21. You Got Lucky, If That's All You Did

It wasn't the gas in the can, i suspect. It was the polymerization of aldehydes and carboxylic acids in the carburetor that plugs things up. The new gas might have just been barely enough to help dissolve the residue and start your mower.

In a gas can, it takes decades to build up enough of these to cause major problems. In the tiny areas of a lawn mower carburetor, the surface per unit mass exposed to oxygen is huge. So, the residue form faster and in tiny ports that will clog.

The stabilizers in gas are, in fact, anti-oxidants, which retard the oxidation reactions of the double bonds along the carbon chain. There just is too much surface area, too much oxygen exposre for those to help much once it's nearly in the engine.