They mix in a corrosion inhibitor to the final product, before it is shipped.
I have a car that has run on 87 with corn juice and it sits with gas in the tank over the winter, and fires up with no issues every year. The only time I put Sta-bil in a tank, I had to clean the carb out the following spring. I haven't done that since, and it hasn't been a problem whatsoever. I've noticed that the Non oxygenated 91 has been grumpy after winter storage, but never that I couldn't fire up the car and drive it.
We've had ethanol in our gas since I can remember, and it hasn't been problematic for many many moons.
