“They might cease to function, but they are not destroyed,.”
One of the other problems is that ethanol will absorb water (humidity) until it reaches about 10% water to ethanol ratio and then drop out of solution.
As posted above, ethanol has a lot higher octane than gasoline so once it drops out, you have a marked drop in octane.
Pre-ignition is the ping you hear from a hot lean engine under load. It does slow damage.
Pre-detonation is fuel detonating prior to the appointed time due to high compression or lack of octane. Pre-detonation removes the tops of the pistons quickly.
That's what's known as "bad gas".
You can't leave it sitting exposed to humidity, or that's exactly what happens. It's not usually a problem in a modern vehicle with a closed fuel system.
Either run your antique vehicle or garden equipment out of fuel, or put Stabil in it, and put the gas cap on with a plastic bag to seal it, when not in use.
Yes, pinging is bad news, same as with a "boost" engine, but the reality of it is, if the water-laden alcohol "drops out of solution" the heavier water falls to the bottom of the tank where the fuel pick up is, and the vehicle probably won't even run, or it will not run well enough to hurt itself.
Don't get me wrong, I'd just as soon have real petrol. It's just that so many wrong arguments against ethanol get put forward...The best argument is:
It takes more BTUs to make it than you can get back out of it.
They make it out West, where the sun shines hot. If they were using that as a heat source, and if the resultant "solar alcohol" made gasoline cheaper...I'd have no problem with it.