Not that we didn't know this.
According to the EPA, ethanol impacts motor vehicles in two primary ways. First … ethanol leans the [air/fuel] ratio (increases the proportion of oxygen relative to hydrocarbons) which can lead to increased exhaust gas temperatures and potentially increase incremental deterioration of emission control hardware and performance over time, possibly causing catalyst failure.
Second, ethanol can cause materials compatibility issues, which may lead to other component failures. What material compatibility issues would they be referring to? Ethanol has been known to wreak havoc on fuel systems, deteriorating plastic and silicone components such as hoses, fuel pumps and filters, gas tanks, and fuel injectors.
Among its other talents, ethanol also has the ability to etch aluminum and magnesium, as well as absorb moisture from the air, allowing a water/alcohol mixture in the fuel tank.