What type of fuel is most commonly used in gasoline engines?

Unleaded gasoline is the most commonly used fuel in gasoline engines due to its wide availability, compatibility with engine designs, and adherence to current environmental regulations. This type of fuel is formulated to provide optimal combustion properties for standard gasoline engines, which are designed to operate on it. Unleaded gasoline is preferred because it reduces harmful emissions compared to fuels that contain lead, which has been largely phased out due to its toxic effects on health and the environment.

In modern engines, the use of leaded gasoline is virtually non-existent, largely due to the establishment of stringent regulations aimed at reducing pollution and protecting public health; thus, it does not represent a viable option for contemporary gasoline vehicles. Diesel fuel, while important for diesel engines, is not suitable for gasoline engines due to significant differences in combustion characteristics. Alcohol-based fuels, though utilized in some applications, are not the standard for the majority of traditional gasoline engines. As a result, unleaded gasoline stands out as the primary fuel choice for gasoline engines today.