Like HowStuffWorks on Facebook!

How the 2008 EPA Fuel Economy Ratings Work

Fuel Economy and the Government
People might be confused by a surprising increase in fuel efficiency between 2007 and 2008.
People might be confused by a surprising increase in fuel efficiency between 2007 and 2008.
JGI/Blend Images/Getty Images

At first, it seems a little odd that the government would measure fuel economy, let alone have two governmental agencies spend time on it. After all, if consumers cared about fuel economy, automakers would test it themselves and advertise the results to gain customers, right? Well, almost. Auto manufacturers do perform their own fuel economy tests, but since it's in their best interests to get the good numbers, each company could perform the tests or manipulate the data in ways that benefit them. The government does the same test on all cars, making its numbers impartial.

The government also has an interest in monitoring the fuel economy of all the cars on the road. Improved fuel economy means less pollution and less dependence on foreign oil. That's why both the Environmental Protection Agency (EPA) and the Department of Energy are involved in testing fuel economy ratings, though the EPA takes a lead role in testing and publicizing the ratings.

Fuel economy ratings have been given out by the government since the 1960s. The problem was that the tests and the ways the ratings were calculated hadn't really changed much since then, despite the fact that cars had changed a lot. Cars can accelerate faster now and have more accessories (like air conditioners) that use extra gas. Highway speed limits are also higher now, and driving faster takes extra fuel. The government changed how it tests fuel economy to take these factors into account.

How did the government change the test to reflect modern-day driving? Read on to find out.