A software method controlling a computer device compares operational performance data collected and stored from a vehicle to a predetermined criterion and determines, based on the comparison, whether to adjust a baseline charge for usage of a vehicle during the period. The software may compare data corresponding to one, or more, different parameters to determine the charge adjustment, the parameters including average MPG, engine revolutions, revolution-minutes, or fuel used during the period. The software method may use average values for MPG for the particular vehicle obtained prepared by a governmental agency. The method may also use criterion derived from governmental information. Or, the criterion may be a predetermined value based on a business consideration, such as number of engine revolutions corresponding to a given number of miles traveled. If the vehicle's engine turns more than the predetermined number during a period, the charge corresponding to use during period is increased.