Aviation gasoline represents the first fuel specifically developed for flight in an era when the spark ignition piston engine ruled the sky. While the industry largely transitioned to the aviation turbine engine many years ago, the piston engine fleet still performs a useful and important role in global transport. Light aircraft represent a unique solution where ground transport is challenged due to adverse terrain, for example by desert, jungle, water, mountains and snow. In addition, the fleet offers pilot training and recreation to promote aviation across the world, foundations on which the wider industry is built. Aviation gasoline is the primary fuel for these aircraft and, in this chapter, the background to the fuel is presented together with its unique attributes, challenges and solutions. Further, details for aviation compression ignition (diesel) piston engines are also included to promote understanding of alternative power sources.