Since you have a highway drive all you need to do in order to get better mileage is drive slower. The EPA tests are still based on a 55mph speed limit and no AC. If you drive faster and use AC your mileage will be lower period. My worst tanks are the one were i drive on the highway at the speed limit of 70.

Keep in mind that you last non-hybrid car was in the same boat and in all likelyhood did not get the EPA rated mileage if you drove it the same way. People just notice the mileage in a hybrid more.

Look at my mileage. The car can do amazing things if you drive it for mileage. My current tank is over 80 mpg. I'll post a picture...

Of course I'm doing all kinds of crazy things to get the mileage up that high including no AC and lots of engine off coasting.

One thing I'd do is get some more air in those tires. What PSI are they rated at? I understand why normal people would not want to give up their AC this time of year but you will hardly notice the increase in tire pressure. Personally I like the feel of the car better with more pressure in the tires.