How are you getting such a high average? I have minimal city driving and get no where near that. In order to get that i'd need to be going 30-45mph for most of my trips.
well when I'm not autocrossing i don't drive hard at all, usually. i would suggest reading tips on ecomodder.com, even if you never modify your car for fuel economy the driving tips posted there are really good. Modifying your driving style is the best mod you can do for efficiency. I used to commute 30miles/30miles and that really boosted my economy average off the bat, i would usually get 45mpg on the way to work, and then around 38-40 on the way back(You have to fight the wind coming home, and you flow with it going there). I used to be at a solid 40mpg average over like 17000 miles, but since i started delivering pizza/autocrossing its going down(i really need a new job).
since i have such a high sample size (21k miles), short trips in the city where i only get like 26-30mpg don't hurt the average visibly because it's not bad enough to bring down that high of miles at a good number. If i were to reset my average and drive for a week, it would probably only be around 34.
as far as easy things to do to improve economy, drive smarter, pump up your tires(my oem street tires are at 50psi cold all around, my autocross wheels sit in the garage until the night before), and dont carry excess weight. People often tell me my car is "so clean" but i just don't carry anything, my glove box has insurance/registration that's it, to give you an idea. I don't carry my spare/trunk lid/or cargo cover, but this is starting to split hairs, other people wouldn't want the inconvenience of added noise or the possibility of needing that spare tire(i have AAA).
Also use high quality gasoline, I'd recommend shell or chevron, for an 8 gallon fill up it's only an extra dollar, and its better for efficiency and better on your internals.