For a gasoline engine to work efficiently, gasoline must burn smoothly without premature detonation, or knocking. Severe knocking can dissipate power output and even cause damage to the engine. When gasoline engines became more powerful in the 1920s, it was discovered that the most extreme knocking effect was produced by a fuel composed of pure normal heptane, while the least knocking effect was produced by pure isooctane. This discovery led to the development of the octane scale for defining gasoline quality.