Underdriving

Underdriving refers to the practice of operating an internal combustion engine at a lower speed than its optimal or designed operating range. This is typically achieved by using a taller gear ratio than would normally be selected for a given road speed, or by deliberately reducing engine RPM. The primary motivation for underdriving is often to improve fuel economy. By keeping the engine speed lower, internal friction and pumping losses are reduced, leading to less fuel consumption. However, underdriving can also have potential downsides. Prolonged operation at very low RPMs can sometimes lead to incomplete combustion, potentially increasing emissions of certain pollutants. It can also put more strain on engine components if the engine is consistently struggling to produce enough power, leading to issues like knocking or stalling. In some cases, underdriving might be a consequence of driver behavior rather than a deliberate technique, such as lugging the engine in too high a gear. Modern engine management systems often have sophisticated controls to prevent excessive underdriving or to optimize fuel efficiency across a wider range of RPMs.