The standards, according to anonymous sources (fearing they’ll lose their relationship with the government body), will be rolled out in two stages by the EPA. Stage One lowers mileage by a certain percentage to reflect air-conditioning use and another other vehicle devices. Stage One affects model year 2008 vehicles.
Stage Two adds three new tests which most likely will lower mileage further. Stage Two affects model year 2011 and beyond vehicles.
These new testing standards reflect reaction by the EPA to auto manufacturers, consumer advocates, and environmental groups who, for some time, have criticized the agency tests which were developed in the 1970s. They claim the tests, whose results are derived from laboratory testing, do not reflect use of air-conditioning or most “real world” driving conditions (e.g., stop/start, bursts of acceleration, etc.) which can cut up to fifty percent of the reported miles per gallon on the window sticker. Hybrid vehicles, such as the Toyota Prius, have especially illustrated this discrepancy.