it is kind of like epa's estimated milage on cars.

 

Mine has always been off 2-4 mpg from hand calc.

 

Mine was pretty close before the 35s... Used to say around 18.8-19.8 now it says 15.6.

 

I don't know why, but when my truck was stock if was always 3-4 mpg off. But since I've installed my Smarty, it is usually within about 1/2 mpg. I get about 17.25 on average in mixed driving and the display says that I'm getting 17.4. It sure beats the 13-14 mpg that I was getting when I was running a Edge Juice w/ attitude.

 

I think it must measure the resistance to roll and calculate that into the readout. I press reset and drive not using the exhaust brake it will stop changing at 17.3, then I'll use the exhaust brake at every chance and it will go down to 15.5. Anyone else with an exhaust brake notice that?

 

with the exhaust brake it wont coast as far maybe thats the difference

 

This is what I have found with my '06 3500. If you press the reset button once, it will go blank for about 3 seconds and average the number that was on the DLD (digital lying device) before you pushed it with what your average currently is getting, and display the average of those two averages. If you hit it twice quickly, it will go blank for about 5 seconds and display what your DLD was displaying pre-push, and what your instantanious (not average) MPG is, and average those two numbers. I know, complicated. I have reset mine repeatedly just playing around on the way to work, and over a two-day period, hitting the button twice while costing in neutral (6-speed), achieved over 50 MPG. Is it correct? I WISH!!!! Is it just a simple Garbage In/Garbage Out computer? Yep. Mine likes to lie a little on the optimistic side, showing 24-24.5 when I calculate 23-23.5 on paper. That's Alaskan summer time. Come winter it'll read 18-19 and be right close to what I'm getting at -40 to -60 degree temps. Nothing like to combust at that temp, especially diesel syrup! You want to see how tough your truck really is? Put it through an Alaskan Iterior for just one winter. After sucking Jello through the filter for 7 months, it will give you a good indication if your truck is a keeper or not!

 

My 06 3500 was staying around 18-19 mpg. Never went below 18 even in town until I started really punching it. Overall I got 15mpg with mostly freeway driving. I filled her up once and turned around and sold her. The other truck I checked out was down in the 11-14 in town and it reacted very quickly.

 

it isnt a instant gauge it is a average gauge

 

Mine reads 3 mpgs higher than I usally get. it reads 21-22 and I actually get 18-19.