EETC Four Stroke Engine Certification Practice Exam

Using a high ethanol blend in small engines typically results in engine damage due to several factors associated with ethanol's chemical properties. Ethanol can absorb moisture, which may lead to corrosion in the fuel system and other engine components. Additionally, higher ethanol concentrations can affect fuel compatibility with certain materials used in the engine, such as rubber and plastic, leading to deterioration and leaks.

Moreover, ethanol has a different combustion characteristics compared to conventional fuels. It can cause an engine to run hotter, which can lead to overheating and potentially result in damage to internal components like the piston, valves, and cylinder walls. The higher volatility of ethanol could also lead to issues with vapor lock, affecting engine performance and reliability.

Thus, while ethanol might seem environmentally friendly due to its popularity as a renewable fuel, using blends that exceed the recommended limits in small engines can lead to adverse outcomes and costly repairs.