The United States Environmental Protection Agency (EPA) laboratory measurements of MPG have consistently overestimated fuel economy.[ This results in a shortfall of about 15 percent in actual vs. measured CAFE goals. Starting with 2008-model vehicles, the EPA has adopted a new protocol for estimating the MPG figures presented to consumers. The new protocol includes driving cycles more closely representative of today's traffic and road conditions, as well as increased air conditioner usage.
The EPA fuel-economy test protocols have changed (to be more stringent) recently. http://en.wikipedia.org/wiki/CAFE#Calculations_of_MPG_overes...
The United States Environmental Protection Agency (EPA) laboratory measurements of MPG have consistently overestimated fuel economy.[ This results in a shortfall of about 15 percent in actual vs. measured CAFE goals. Starting with 2008-model vehicles, the EPA has adopted a new protocol for estimating the MPG figures presented to consumers. The new protocol includes driving cycles more closely representative of today's traffic and road conditions, as well as increased air conditioner usage.
The new (second generation) Honda Insight only achieves an EPA rating of 41 MPG combined. http://news.google.com/news?q=honda+insight+mpg