When oxygenators came to gasoline here on the West Coast, Arco brought out MTBF. Cut gas mileage, and had a short shelf life, and if it spilled and got into the lake, it killed fish people fished for and ate for dinner.
We now have lakes where you are mandated to run MTBF free fuel. We now have lakes where 2 stroke boat motors are no longer allowed. We now have crappy gas, also.
As a boy mowing lawns in the 1970's, the Honda mower my dad bought for me to push never had carb problems. That changed around 2003 or 2004. I drain the fuel tank come fall, or when I think it's the last mow job of the year. Gas quality in storage has declined a lot.
The West coast does not have access to huge cornfields to make alcohol out of... all our corn goes into corn chips, corn meal, corn tortillas, etc, so it took a long time for us to start seeing cut fuel with alcohol in our fuel supply.