Ethanol isn't blended in at the refinery because we don't want our equipment like tanks and pipelines damaged.Once you get over 10% corn alcohol in pump gas, it's death for small engines and there is no way in reality, a gas station owner will know because the corn alcohol is blended in at the refinery and you are 100% at the operator's mercy at the refiner. Modern ECM controlled engines can internally compensate for it and so can 'flex-fuel' engines. Small engines and motorcycle engines cannot. Why I switched to canned gas a while ago. No guessing, no issues and best of all, canned gas smokes very little and the exhaust don't stink either... and no carbon buildup on the spark screen or in the exhaust port-tract either.
I'd never buy any pump gas for my saws or brush trimmer, ever again. Far as my small 4 strokes like the rototiller and lawn mower, I add some ATF to each tank just in case.
In fact I just dumped 8 gallons of gas I bought in the fall into my ECM controlled car. It can adjust for the stale gas.
It's blended typically at the loading rack.