The city and highway tests are currently performed under mild climate conditions (75 degrees F) and use acceleration rates and driving speeds that EPA believes are generally lower than those experienced by drivers in the real world. Neither test is run with the use of accessories, such as air conditioning. The highway test has a top speed of 60 miles per hour, and an average speed of only 48 miles per hour.
if you drove 48 miles per hour average on the highway, you would get what they say you will..