The computer is pretty spot on in my 06 3.5L I calculate manually about once a month, and its never been more than .5 MPG off.

I think the absolute lowest i've ever got out of my 06 3.5L was about 22 MPG, I am usually up in the 25-26 range, and it will do 30+ on long road trips if I keep it under 80 MPH.

With the 10 min idle time, and the 2 mile trips, 14 sounds about right. You really should make an effort to drive the car on the highway every once and a while to really get everything up to operating temp.

 

Well today I filled it up for the first time since I got it (man that's a big tank lol) and went for about a 20 mile drive in it, probably the furthest I've taken it since I got it. I just don't drive it a lot since if the wife and I go somewhere, usually it's in her '06 Vue since she hates how low cars sit. When I got it, I reset the average speed on it and before I took the drive today, it was at just 13.7 mph, when I got back, up to 14.3 so I guess I stretched her legs out a bit.

Anyways, I'll run this tank out and hope it improves. 10 minute idles are done with. I can deal with the cold for two minutes if it's saving gas.

 

Yea, that low of an average speed definitely shows that your car is a city car! 80% of my driving is highway, at speeds of 75+, and my average speed over the last few months is 53.4 MPH right now.