I was doing a little research on fuel efficiency to respond to a comment on an earlier entry. I wanted to find out how the EPA measures City/HWY. I think I know why lots of people are finding the EPA numbers hard to match. from The test to determine the highway fuel economy estimate represents a mixture of "non-city" driving. Segments corresponding to different kinds of rural roads and interstate highways are included. The test simulates a 10-mile trip and averages 48 mph. The maximum speed is 60 mph. The test is run with the engine warmed up and has little idling time and no stops (except at the end of the test). So does that sound like the highways that you drive on? The EPA says about -7% for every 5mph over 60mph, worse for bigger vehicles, and that number is obviously non-linear. Checkout for some math. I won't put actual numbers on how I drive, but I will say that a significant amount of traffic traffic travels well beyond the posted speed limits, and way way faster than the EPA test averages. 80mph+ on interstates is pretty common, and 65+ everywhere else seems more likely. No way in hell you'll see EPA numbers at those speeds.