Abstract: A system and method for monitoring engine performance utilizes a monitoring micro-controller that integrates with an engine/vehicle controller to receive data indicative of the current operating conditions of the engine/vehicle. A duty cycle map is defined within the micro-controller by a plurality of sectors bounded by a specific performance curve based on two or more engine operating parameters, such as engine torque and speed. Each sector corresponds to a range of values for the specific operating parameters. During iterations of the monitoring routine, current data indicative of the specific engine operating parameters is sensed and compared with the range of values for each duty cycle sector. A duty cycle parameter, such as elapsed time or fuel consumption, is maintained for each sector. When the current engine operating conditions fall within a particular target sector, its corresponding duty cycle parameter is updated.