http://media.gm.com/content/dam/Media/documents/US/PDF/fuel_economy.pdf A lot is the usual marketing fluff and emphasis on EPA highway numbers. GM seems pretty good at optimizing for the EPA tests which apparently doesn't return such good results in the real world or other tests (Why The Chevy Equinox EPA Mileage Numbers Don’t Add Up | The Truth About Cars, for example). The term "active fuel management" is another annoying marketing term they use. The correct non-marketing term is cylinder deactivation. For reference, take a look at how GM does vs. the 3 major Japanese automakers for their 3 fleets (IP, DP and LT) at http://www.nhtsa.gov/staticfiles/rulemaking/pdf/cafe/October_2011_Public.pdf.