Hey guys I'm at the end of my rope here.
I have a 06 Dually auto with 4:10 gears
I have put 35" tires on it
I have replaced the injectors
All the filters
It has 135000 miles
I recently installed efi live

My problem I still only get like 9.8 mpg that's hand calculated
I'm open to anything at this point
Oh yeah I drive it like an old man

So where or what do I do from here

 

a cam change to a pdr or colt II should get you 2 mpg. efi live needs someone who knows how to write the tune, contact anarchy. on the auto I hate them so bad I can't help but someone on here can tell you if a lockup device would help, selling it for scrap and getting a g56 will help more.

 

Bigger exhaust and better intake?

 

Crafty, always go back to the basics when something craps. First, do you have any codes? Can you remove the efi live while you diagnose the engine? Have you had the program checked by the guy who wrote it? Having replaced the injectors, have you had a computer hooked to it to tell you if they're functioning correctly?

 

your 06 has a better intake than a aftermarket. a bigger exhaust helps a little but not your problem.

 

Have you had the speedo re calibrated? With 35s, you are not racking up miles on the speedo, so calculating with less miles traveled than actual will show worse mileage

 

When did your MPG`s go to hell?
Has it always been that bad or after the mods?

 

9.8 is bad. In fact so bad, I don't believe it. Check your speedometer with your Sat Nav. Make sure it's correct. Your ECU has a divisor that is used to divide the pulse count emanating from the hall effect sensor in the diff. Decreasing that number increases the odometer count and speed on the speedometer. You will need the dealer computer to do it, but it is easy to change. I would advise to compute the exact error in percentage you observe. Then divide the number read by the computer by your error percentage. Then subtract that number from the one you read. That result is the one you put back into the computer.

The manual says that the number in the computer is feet rolled per mile, but the arithmetic does not work out that way. (I measured it) The percentage thing does work well for me, but I admit, I had to adjust that number several times until I finally got it correct.

 

Anyone with a Smarty can adjust your tire size and it will "stick" after removing the program. The '06-'07's do that. Prior to those years,the abs will reset to stock upon removal of a Smarty program.
As mentioned using a GPS will enable you to check the accuracy of your odometer. The 35's certainly don't help especially MT's if you have them.