I think a good part of the problem may be your very short commute. My TL's mileage is terrible until it warms up. If you're only driving a few miles, then the car sits all day, then another few miles at the end of the day, all on a cold engine, you're essentially driving in the worst possible MPG conditions. You're never getting the car up to full operating temps for maximum efficiency.

As a side note, really short trips like these are engine killers. The condensation that builds up as the engine heats/cools is never fully burned off and is free to do its damage to the engine parts. You should try to run the car on longer trips at least once a week to try to counteract some of that.

 

This is a follow up for Aik. Just did a 240 mile trip mostly highway in the 2010 MDX. Got 6600 miles on the clock so I'm fully broken in. I'm running full synthetic oil and used premium gas. Also had a full load of luggage in the trunk and 3 adults.

The first 120 miles got me about 21.9 mpg from the trip computer. The second 120 miles with a few short jams on the highway got me 20.5 mpg. So overall I'd say the MDX is performing within spec. Hope you're getting a better experience now than before Aik.

 

I have a 2009 MDX with 23000 miles and on a highway trip this past weekend I got 26.5 mpg - but the driving conditions were perfect.

 

My 2011 MDX Advance {now broken in} is getting 16.0 city and 23.0 highway with a 50 - 50 mix of 93 prem and 89 plus. Trip meter checks out correct w actual mileage driven per mile 1,2,3 signs or known length test track. You need to verify this first.

If you get less ... its your driving habits and style.
Drive fast / hard on short trips and you get screwed.
Also ... what you with it is more important than MPG.
Combine trips and cut your total miles driven.
If that dont make you happy drive a lighter compact etc.