What is the effect of using a significant percentage of alcohol in fuels?

Using a significant percentage of alcohol in fuels, such as ethanol, tends to lean out the carburetor. This is primarily due to the oxygen content in alcohol, which results in a more complete combustion of the fuel mixture. When alcohol is mixed with gasoline, it can create a blend that requires a different air-fuel ratio, often leading to the necessity of adjusting the carburetor settings to optimize performance. If the carburetor settings are not adjusted accordingly, the engine may run lean, resulting in incomplete combustion and potential engine performance issues.

When alcohol is added to fuel, it can also absorb moisture from the air, which affects the overall combustion properties and stability of the fuel, leading to the need for careful tuning of the fuel air mixture. This lean condition can cause various operational issues, such as overheating and potential damage over time if not addressed.

While the other options may seem plausible in different contexts, they do not accurately describe the primary effect of alcohol in fuels. Increased fuel efficiency, reduced engine temperature, or enhanced fuel stability are not typical consequences associated with high alcohol content in fuels without considering the necessary adjustments to the engine’s air-fuel mixture and system.