How Vehicles Are Tested

Fuel economy is measured under controlled conditions in a laboratory using a standardized test procedure specified by federal law. Manufacturers test their own vehicles—usually pre-production prototypes—and report the results to EPA. EPA reviews the results and confirms about 10-15 percent of them through their own tests at the National Vehicles and Fuel Emissions Laboratory.

In the laboratory, the vehicle’s drive wheels are placed on a machine called a dynamometer that simulates the driving environment—much like an exercise bike simulates cycling.