The 2.7T in my wife's old Edge never got the posted mileage for city.
The EPA test is bogus anyways. The highway test for example is for 10 miles at an average speed of 48mph and doesn't exceed 60 mph. That's too slow as most people drive 70-80 on the expressways. If you are doing 60mph on 355 for example, you're going to be getting passed everyone.
The EPA Highway test is only one of 5 tests. Before 2008 there was only the City and Highway cycles. They were poor at estimating fuel economy and were about 20% too high for the highway. Since they added the three supplemental tests, they are much better. The US06 cycle tops out at 80 mph.
The window sticker uses the five. It's very close to real world. CAFE numbers still use the 2 cycles. So when they say 54 mpg, they really mean 45 real world.
I would not consider 355 "highway" driving. Highway driving is putting on the cruise control and going long distances. Yes, you go 80-90 on 355, but then nail the brakes every time your cut off and then hammer the throttle to get back up to 80 mph. It's high speed city driving.
Based on my understanding, the EPA tests vehicles in a lab on a dyno for fuel economy ratings. That's not realistic for various reasons (wind resistance/coefficient of drag, friction of tires on road, etc.).
well and past that how do you account for 17 different wheel/tire combos, different gearing options, different alternator setups, cab configurations, seat packages, etc, all create different loads on the engines/weights on the vehicles.