A method for improving fuel efficiency testing precision in on-road vehicles. The method comprises: installing one or more dataloggers in one or more vehicles, each datalogger configured to receive fuel consumption data broadcast by an on-road vehicle's engine control unit (ECU); transmitting the fuel consumption data from the one or more dataloggers in the one or more on-road vehicles to a processor; and analyzing, using the processor, the fuel consumption data from the one or more dataloggers in the one or more on-road vehicles to determine fuel efficiency of the one or more on-road vehicles. The fuel consumption data comprises fuel rate data from the ECU which is transmitted through the one or more dataloggers, engine speed and other operating parameters from the ECU that are transmitted through the one or more dataloggers, torque sensor data which is transmitted through the one or more dataloggers, and traditional fuel log data.