Not getting the MPG I think I should

So, my normal commute is 37 miles one way, with about a 2000 ft elevation gain on a 2 lane road. I've had worse commutes... That being said, I've been averaging about 33 MPG per tank. Ok, I understand with the mountain, that's not bad. But over the weekend, I took interstate from home to Black Mountain, NC. I-77 to I-40. Even with cruise control set most of the way at PSL (70, then 65) I only got 37 MPG average. On the way home, the trip started down a big mountain, so I was able to average 42. Not as good as I was expecting.
What items should I be looking at on my 2014 CTD?
I've already:
Changed all filters except the fuel filter. (Dealer changed that right before delivery, there is still 47% life on it.)
Put in amsoil oil and transmission fluid. (Flushed transmission)
Cleaned the MAF.
Tightened the 5 hose clamps from the air filter onwards.

I was thinking maybe have the dealer:
Reset the LTFT
Flash the HVAC (I have the humming noise when the car shuts off, and if I maintain 70 or greater with RPMs 2K or over, the A/C shuts down - but that's another story.)

Any other things I should consider?