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It is well known that as the weight of some automobile subsystems is reduced, there is the potential for further reduction in total weight. In preparing an estimate of automobile fuel economy in the post-1985 period, it became necessary to estimate approximate overall weight propagation factors suitable for such an analysis. The derivation of the factors is based on separating total automobile weight into weight sensitive and weight insensitive parts, and developing regression equations for the weight sensitive part. The data used to develop the regression equations were taken from the literature on weight propagation, and from National Highway Traffic Safety Administration (NHTSA) sponsored vehicle teardown studies. Two factors were determined, one for a totally new vehicle, and another for upgrading an existing design.

A simple model of the energy required to negotiate the two Federal test cycles is described and then used as a bssis for a graphic representation of the relative energy consumption. The utility of the concept is demonstrated by comparing certification fuel economy data and projections with the aid of the relative energy consumption plot.

Skeleton production plans are developed for several scenarios. Weight estimates are made of each “base level.” Engines and transmissions are matched to the new weight, and a value of fuel economy, without other technological improvements, is determined. Fuel economy improvements due to other technological changes such as reduced aerodynamic drag, reduced tire rolling losses, the application of improved lubricants, etc., are added. Annual fuel economy estimates, by manufacturer, for each scenario, result. A brief review is included of the evolution of this methodology.