The shelf life of current gasoline is only about 4 months.

Swell.

That gives us a great feeling for the (topless)(white) car that sits in the barn, for the lawnmowers, and other gear.

I expect that water will make the gas more corrosive, too.

Yeah, we’ve been thinking about that as well. And consider that the South Puffin air that brings the water into the gas tank is salt laden.

At the least, I suggest you run the Keyscar tank empty and then fill it with fresh

Good idea except for the leaks. Maybe I’ll just fill it wth Stabil™.

I need to think about that for my motorcycle, which also goes months without running.

And its hoses.

… including in your gas tank, over time. But now it migrates to the ethanol, and when the ethanol dissolved in the gasoline gets enough water content, it becomes immiscible with the gasoline and separates as very small liquid particles which stay suspended. Since ethanol/water solution has a refractive index different from gasoline, the fuel appears cloudy. I am guessing that the viscosity is also higher because you have separate phases. Has to affect fuel metering, even with a carb.

A friend bought a dump truck with a crate motor that had been sitting quite a while. It would start and idle but wouldn’t run well. He pulled a gasoline sample and found it to be cloudy. Drained the tank, flushed it, then filled with new gas. Truck fired right up and runs like a champ. He says he’s heard that the shelf life of current gasoline is only about 4 months.

I expect that water will make the gas more corrosive, too.

At the least, I suggest that before leaving [South Puffin] you run the Keyscar tank darned near empty and then fill it with fresh gas. You might add Stabil™ as well.

I need to think about that for my motorcycle, which also goes months without running.

Be aware that the mechanisms described fit the evidence, but that alone cannot confirm causality. When I offer explanations like this to some folks, I tell them “I’m free-lancing” i.e. I am offering highly-educated speculation, not reciting established and well-proven fact.