A method for characterizing a vehicle's fuel efficiency including generating parameter-related data from the vehicle that describes at least one of a plurality of vehicle parameters including: vehicle speed, fuel level, engine speed, load, mass air flow, manifold air pressure, odometer reading; transferring the parameter-related data to a wireless appliance including a wireless transmitter; transmitting the parameter-related data with the wireless transmitter over an airlink to a host computer system; and analyzing the transmitted parameter-related data with the host computer system to calculate the vehicle's fuel efficiency, wherein the analyzing involves determining an amount of fuel consumed by the vehicle during an interval, determining a distance traveled by the vehicle during the interval, and calculating the vehicle's fuel efficiency from the amount of fuel consumed and the distance traveled during the interval.