Magnum Fuel Rx is a device that attaches to a vehicle's fuel tank and uses radio frequency waves to alter the atomic signature of gasoline, making it burn more efficiently and provide benefits like increased fuel economy, horsepower, and reduced emissions. It works by making standard 87 octane gasoline perform like higher octane gasoline without needing to purchase more expensive fuel. The document provides details on how Magnum Fuel Rx works and its benefits over other fuel-saving methods. It claims users can achieve fuel efficiency improvements up to 40% and that it is risk-free to try for 45 days.