Abstract: An easily installed versatile trimmable fit-to-size vortex airflow generator for use in internal combustion engines to enhance fuel efficiency is provided. The multi-impeller vortex generator comprises a plurality of blades evenly spaced angularly on a central hub. The blades are a ready trimmed to size to fit within the air intake conduit of most, if not essentially all, known conventional internal combustion engines. The vortex generator is constructed, i.e., formed, of a non-rigid construction such as molded plastic that is readily inserted in engine air intake passages to enhance turbulence.