What type of fuel is commonly spark-ignited and used in small engines?

Gasoline is the most widely used fuel in spark-ignited internal combustion engines, particularly in small engines such as those found in lawnmowers, chainsaws, and small automobiles. This type of fuel is specifically designed to vaporize easily and ignite through an electric spark produced by the engine's spark plugs. The chemical composition of gasoline allows it to combust efficiently in these engines, providing the power needed for their operation.

In contrast, natural gas can be used in some modified engines, but it is not as commonly utilized in small engines due to infrastructure and availability issues. Diesel fuel is associated with compression-ignited engines, which operate differently than those that use spark ignition. Ethanol, while it can be blended with gasoline and used in small engines, is not typically the sole fuel choice. Thus, gasoline's properties and compatibility with spark-ignited engines solidify its status as the most common fuel used in small engine applications.