Cruise control can kill mileage when the road isn't straight and flat.
Also, winter gas will easily get you 2-3mpg less vs summer gas, sometimes it's even worse.
Also, the combined rating for your vehicle should be about 31 mpg. the 38 rating is for highway ONLY, and any city driving will bring that down considerably.
Also remember that EPA estimates are based off conditions most drivers never encounter. Driving above 60-65mph on the highway will start killing mileage as well, and taking too long to get up to speed can also negatively effect mileage in many cases.
In short, the EPA ratings are junk and should be used solely to compare different vehicles, and rarely represent actual mileage you will obtain.
Hatch Nation #29