Maxx Fuel, an internal combustion catalyst, contains a group of rare earth compounds, including cerium oxide, unique in reducing fuel consumption. Maxx Fuel can reduce fuel emissions up to 60 percent and boost engine performance up to 22 percent, according to independent testing. Maxx Fuel's simple design allows for easy installation on most engines. The device is mounted near the engine and connected to the engine's air intake with a rubber hose.