In the 1960s a city loop in the Los Angeles basin was used to test vehicles for fuel efficiency. Later on, in the 1970s, fuel economy estimates were officially introduced as a way to assist new car shoppers with their purchase. Instead of using real-world driving conditions, the EPA began to use an indoor dynamometer to conduct two laboratory tests designed to estimate fuel economy. The tests were conducted at around 75 degrees F, and included acceleration rates and driving speeds that the EPA believed to be lower than those expected in real-world conditions. In addition, the tests were conducted with all accessories, such as air conditioning, turned off. As for the highway test, it was conducted at 60 mph with an average speed of only 48 miles per hour. After the tests were conducted, the results were adjusted downward for all vehicles – 10 percent for city and 22 percent for highway -- to more accurately reflect driving styles and conditions. How’s that for real world calcuations?
New EPA Fuel Economy Estimates
In 2008, the EPA decided to get with the program and base its estimates on more accurate information. Using revised calculations, the new EPA fuel economy estimates take into account conditions that can significantly impact gas mileage.
This includes:
- High speed/rapid acceleration driving
- Use of air conditioning
- Cold temperature operation
In 2011 the EPA will take things a step further by requiring manufacturers to perform even more actual tests as opposed to the revised calculations introduced in 2008. This means we should begin to see even more accurate results as time progresses.
As such, the new EPA fuel economy estimates differ slightly from previous calculations. You can examine the new estimates for all Mustangs current through to 1985 in my Mustang Fuel Economy Estimates Database.
