An apparatus is provided for diagnosing the state of health of a vehicle and for providing the operator of the vehicle with a substantially real-time indication of the efficiency of the vehicle in performing an assigned task with respect to a predetermined goal. A processor on-board the vehicle monitors sensors that provide information regarding the state of health of the vehicle and the amount of work the vehicle has done. In response to anomalies in the data from the sensors, the processor records information that describes events leading up to the occurrence of the anomaly for later analysis that can be used to diagnose the cause of the anomaly. The sensors are also used to prompt the operator of the vehicle to operate the vehicle at optimum efficiency.