The coefficient of drag is part of the rolling losses equation for sure, but other factors also play a part. The method we use starts with a polynomial equation for rolling losses for a vehicle. The factor entered into the software is plugged into this equation to arrive at all rolling losses values from 0-MPH through the maximum MPH of the dyno. The factor is the hp losses at 50-mph, one point on the MPH losses curve. The rest of the losses curve is extrapolated via the polynomical equation. The methods employed by our system were established by the Society of Automotive Engineers (SAE) and the EPA.