My lawnmower is going on 8 years on e10 with no issues.
I’ve had lawn mowers run OK on E-10 also. Other small engines may not fare so well, as in the case of the power washer I got back from fuel system repairs last week. The guy that did the work diagnosed the problem via e-mail, and had it fixed in a couple of hours. His advice: avoid E-10 in this particular small engine, because in the local environment (Houston), where the ambient atmosphere consists of 78% liquid water, all of that water will end up in your gas tank just as surely as if you had filled the gas tank from the garden hose. So, if your advice to me is to use E-10 in my newly repaired power washer, you’ll forgive me if I politely decline.