What is your opinion on using a 90/10 blend of gasoline with ethanol in small engines?
In new engines I wouldn’t worry too much unless the manufacturer says something specific about it. Most manufacturers say up to 10 percent ethanol is OK. Some recommend draining the fuel if the engine is going to sit for long periods. In older engines, keep an eye on rubber components such as fuel lines. If they aren’t ethanol compatible they might change shape or consistency after contact with the fuel. I have experienced some leaking/hardened lines in older Briggs and Kohler engines, but my newer engines handle the gasohol just fine. I just replaced the leaky lines on those older engines and have had no other trouble. Theoretically you could have fuel pump trouble (if the engine has a diaphragm pump) and carburetor gasket issues, but I am not aware of any significant problems. Plenty of controversy surrounds gasohol, but it has been around for a long time. I have used it in every gas engine I have had since the mid 1980s or so. Methanol-laced fuel is a slightly different story though, because wood alcohol is an incredibly powerful solvent and highly poisonous to boot.
— Oscar H. Will III, editor, GRIT magazine