An exhaust gas temperature gauge (EGT gauge or EGT sensor) is a meter used to monitor the exhaust gas temperature of an internal combustion engine in conjunction with a thermocouple-type pyrometer.
By monitoring EGT, the driver or pilot can get an idea of the vehicle's air-fuel ratio (AFR).
At rich air-fuel ratio, the exhaust gas temperature either increases or decreases depending on the fuel.
High temperatures (typically above 1,600 °F or 900 °C) can be an indicator of dangerous conditions that can lead to catastrophic engine failure.
However, some advanced racers[example needed] will use EGT gauges in combination with a wideband oxygen sensor to lean the fuel ratio a bit to safely raise the temperature for more power.