“But we’re talking gasoline/alcohol fuel applications”
Yes we are, and evaporated Gas/Alcohol molecules are smaller than any gasket/O ring materials used. Over time they leak out right between gasket molecules. Alcohol much faster than Gas because the molecules are even smaller.
“Modern cars have a sealed fuel system.”
Still not sealed. Let a “sealed fuel system” car sit for six months and then smell the gas. It will still be varnish because of evaporation. The cap gasket, O rings, and vacuum lines still leak on a molecular level.
“Modern engines use neoprene not rubber.”
I was referring to tires as a comparative material. Cars use neoprene, nitrile, silicon, urethane, and paper gaskets and seals. All still have larger molecules than alcohol molecules.
An example of this reality would be sealed auto A/C systems. Even though Freon molecules are much larger than Alcohol molecules they still leak out through the O rings and hoses over time.
This may be true to a fractional degree, but nothing like that of a vented container. The issue I was addressing is not fuel evaporation, but keeping the water out.
Still not sealed. Let a “sealed fuel system” car sit for six months and then smell the gas. It will still be varnish because of evaporation. The cap gasket, O rings, and vacuum lines still leak on a molecular level.
Maybe, but they're pretty much airtight. I've never experienced this. (nor heard of it) My bikes and older vented vehicles will produce varnish, absorb water and rust out the tank.
I've kept gas in a typical, well worn, plastic utility can for long periods of time, maybe even a year...the gas has never gone bad, and is always consistent, no matter how full it is.
My whole point of posting is: to those guys who say "gasahol destroys engines"....no it doesn't, but the water it attracts will cause fuel system problems on older gear.