Every day on this site I see countless posts by users complaining that the gas mileage their trucks are getting isn't matching what the window sticker rating stated the truck would get. There is also a lot of speculation about how the EPA tests, but I have heard only a few posts that actually convey the true testing procedure. I think a lot of the confusion surrounding the ratings is rooted in the lack of understanding regarding the testing procedures that the EPA mandates. These numbers aren't calculated by actually driving the truck around a track or on the road. There would be too many variables to have repeatable results that would have a uniform procedure for all cars.
The EPA gas mileage numbers are calculated through the following procedure by each individual company and randomly verified by the EPA:
Vehicles are driven on a dynamometer in a controlled laboratory setting (in order to eliminate weather and road variables
). Both city and highway driving are simulated.
The city test is a 7.5 mile trip lasting 23 minutes with 18 stops, at an average of about 20mph. About 4 minutes are spent idling (as at a traffic light), and a short freeway segment is included. The vehicle begins the test after being parked overnight at about 72˚F.
The highway test is a 10 mile trip with an average speed of about 48mph. The test is initiated with a warm engine (following the city test), and is conducted with no stops and very little idling.
In 2008, the EPA also added three new tests. these included:
1) A high speed test (still only averaging 48.37 mph but now including a few short spans reaching 80mph.
2) an air conditioning test, where the ambient temperature around the vehicle is increased, the AC is turned on, and the vehicle averages 21.2mph.
3) A cold temperature test, where the vehicle is cold started in a lab that is 20˚F and driven an average of 21.2 mph.
graphs of each test can be located here
In the real world, one needs to factor in weight changes based on packages, wind, road surface, tires, gears, aerodynamics of different packages... the list goes on. All of these things change depending on the vehicle configuration you buy or the environment you drive in. It would be impossible for ford or any other company to test each package and give results accordingly (if you've used ford's online builder you know just how many combinations there are). Ultimately, the testing procedures should probably change to reflect a more realistic view of driving (mainly speed) but for now, I would just like to hopefully clear up how the results are actually obtained. Please feel free to add anything else you know as I am not the end all source on this subject! Hopefully this post will be informative to people and help to clear up some of the debate. In the end, people need to understand that the results from the EPA are not a guaranteed rating for real world driving and that it is unrealistic to expect to obtain them on a daily basis. Instead just go out and enjoy your awesome trucks and stop complaining about the numbers!