Mitsubishi A6M2 (Zero). US Air Force photograph of a test flight of a captured Japanese Mitsubishi A6M2 (Zero). This aircraft was being refined and improved by the Japanese during the final days of World War II (1939-1945). They increased the low octane rating of their gasoline by adding ethanol to the fuel. The Mitsubishi Zero was already a feared fighter aircraft, and this higher octane fuel helped to improve engine performance.