@rocket
All gasoline type fuel will "varnish". This happens when the light hydrocarbons evaporate.
When I store lawn equipment or the motorcycle for the season. The fuel tank is filled with fresh fuel and a dose of fuel stabilizer. Carbs are run dry and drained. When the storage time is over, the fuel tank is drained and replaced with fresh fuel. The drained fuel gets added to the truck's tank, then the truck is topped off at the gas station.
At most, about 2 gallons of "old" fuel will be mixed with roughly 18 gallons of fresh fuel. The truck doesn't notice.
I can't speak for every situation, only my experience. I've been doing this practice for more than 40 years.......I'm gettin' old. I have never had problems with 10% ethanol fuel in any of my engines. Currently, there are 7 fuel burning engines at this house with ages running from 1981 to 2019.
Something to consider. There are literally 10s of thousands of vehicles burning 10% ethanol. If the fuel has the dire consequences as claimed on the internet, then most of these vehicles would be in the shop or disabled along the road. Sure, there are always the outlying examples that are extrapolated to include all vehicles.