the epa doesnt really test a wide range of cars, so i might argue that quality control has something to do with so many different owners reporting vastly different numbers under similar conditions. i might argue that nobody has had better quality control over the past two decades than honda and toyota.
the epa tests are far from perfect, but starting in 2012 manufacturers will be required to actually run cars throught tests that will include factors such as ac use, hard accelerations and cols start ups. since 2008, these conditions have only been simulated by plugging the pre 2008 tests into a formula to simulate those conditions. thats when all the epa rating went down by roughly 4 mpg's. it wil be interesting to see what happens to all the numbers when the numbers are a result of the actual tests.
cars that are more slippery are going to be hurt less at 75 mph than others (hatchbacks are always at a disadvantage here).
the sonic should get over 40 no problem. i stated at 75 mph it will not get in the low 40's because of its drag. im sure at 55-60-65 it should beat epa hwy numbers.
all cars since 2008 should be beating the epa hwy numbers by at least 1-2 mpg's unless drivers are really thrashing their cars.
its a guarantee, though, that there will be drivers that drive like a**clowns, then come to the forums complaining they are only getting 24 mpg's.
i should disclose that (in my mind) subcompact sedans dont exist and should only be made so that rental companies have something to rent. if a presidential candidate promised to abolish subcompact sedans, id vote for him.
so, when i discuss the sonic, i only see the hatchback in my thoughts. however, i respect the right of a person to drive the sedan.