Source: Consumer Watchdog
quote: 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.
quote: Reliable numbers from one of these sources is better than the dog and pony show that the EPA is putting on with their tests of prototypes.
quote: I own a2011 Sonata 2.0t. It's rated at 22/33/26 (city/highway/combined). Although my combined numbers are pretty much in line with where they should be, I have NEVER, EVER gotten 33 mpg on the highway after over a year with the car and 15,000 miles. That's even when I set the cruise and do between 65mph and 70mph .
quote: The EPA highway figure is derived from a test which (except for the start and stop and some brief periods in between) is between 50-60 mph.
quote: The reason why fuel economy estimates have been coming out too high is simple: The EPA-specified testing and reporting method has not been updated since 1985. Since then, a lot has changed. For one thing, the former national speed limit of 55 mph has been abolished. So instead of topping out at 60 mph, the new highway rating test includes speeds up to 80 mph.