http://www.nhtsa.dot.gov/cars/rules/cafe/overview.htm "Manufacturers can earn CAFE “credits” to offset deficiencies in their CAFE performances. Specifically, when the average fuel economy of either the passenger car or light truck fleet for a particular model year exceeds the established standard, the manufacturer earns credits. The amount of credit a manufacturer earns is determined by multiplying the tenths of a mile per gallon that the manufacturer exceeded the CAFE standard in that model year by the amount of vehicles they manufactured in that model year. These credits can be applied to any three consecutive model years immediately prior to or subsequent to the model year in which the credits are earned. The credits earned and applied to the model years prior to the model year for which the credits are earned are termed “carry back” credits, while those applied to model years subsequent to the model year in which the credits are earned are known as “carry forward” credits. Failure to exercise carry forward credits within the three years immediately following the year in which they are earned will result in the forfeiture of those credits. Credits cannot be passed between manufacturers or between fleets, e.g., from domestic passenger cars to light trucks." I do wonder though if the CAFE credits can be transferred if one company owns the others. Can Ford transfer their CAFE credits amongst Ford, Lincoln, Mercury, Mazda, Volvo, Jaguar, Land Rover, & Aston Martin? The CAFE wording sounds like this could be done but understandably not between 2 entirely different auto companies like Ford and Honda. That does make sense actually though I have no idea if it is true or not. An auto company would want as many CAFE credits as possible to offset CAFE penalties on all of their other brands that get less than 27.5 MPG. Also, if it is true, it would make perfect sense from the manufacturers' perspectives to use the lightest oil possible that is easy for the public to get (5W-20) in order to cut CAFE penalties and also rack up CAFE credits.