With EPA rat­ings posted on win­dow stick­ers and automaker web­sites, it is inter­est­ing to note that only about 15 per­cent are ver­i­fied by regulators.

Even then, actual results vary from vehi­cle to vehi­cle, model to model and dri­ver to dri­ver. Automak­ers do their own test­ing first.

Up to a 3 per­cent vari­a­tion between man­u­fac­turer and the EPA is per­mis­si­ble. After that, penal­ties kick in.