2010 Toyota Prius – Click above for high-res image gallery

Ever wonder what actually goes into determining the rated fuel economy of a new car or truck? Anyone with a vehicle that's failed to live up to its EPA estimated figures would surely fit into that camp – especially if the car or truck were purchased in large part to its high mileage rating – and you can add our names to that list as well. As it turns out, the process is every bit as as complicated as we'd expect.

Car and Driver recently hung out at the EPA's testing facility near the Motor City, and some highly intriguing bits of information were gleaned. For instance, C/D says that just 15 percent of new cars get tested by the EPA each year for fuel efficiency, and the rest get their ratings from testing performed by the manufacturer using the government agency's guidelines. It's reportedly rare that the EPA's figures vary greatly from the numbers provided by the manufacturer, but if they do, discussions and negotiations ensue.

There are a total of five tests performed to measure expected fuel efficiency, some dating all the way back to the late Seventies. More recent protocols are a bit more complex and require specialized facilities that can cost up to $10 million dollars by EPA estimates. There's plenty more to the story, so click here to read the full four-page report. Hat tip to Julio!


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[Source: Car and Driver]