One of the things hurting my milage is that I have 4.10s, and of course the 35" tires don't help, except with keeping the RPMs down a bit.

 

For 2006, if you can keep the rpms below 2000 rpm, tires inflated well, summer tread, and drive at 60 degree temperatures or above, you should be able to reach 22 mpg highway.

For point of reference, I typically drive 70 mph which is roughly 2100 rpm with manual G56 and 315s, megacab, rolling terrain. Warm weather empty mileage (measured) is 20 +- 1. I've seen as low as 15 mpg in cold weather (10 degree high temps). Some fuel additives help a bit, but outside temperatures and rpms seams to have the most influence... oh I suspect towing heavy may also have some influence. Lowest I've ever seen over a tank is 13, lots of idling and in town hauling on half of that tank.

Starting 06 there is no instant (current) mpg reading on the overhead. You see the calculated average mileage since manual reset. Reset the reading coasting down hill and I can see 65 mpg.... as long as I'm coasting. My overhead mph is consistently 10% low of actual measurements, but they varry from truck to truck.

 

wow...i just got back to Washington Dc from Tampa,FL.......let see,
i was pulling a jetski, full thank of Diesel, 75mph, the most was 450 miles.
one time i was driveing 500 miles with 65mph.

what should i get to have better gas mile on my truck

 

75 is gonna kill your mileage, I know it's hard to drive slower, but other than mods you are not gonna see much better.

I get 500 plus on a tank commuting before my light comes on which means approx 10 gallons left since I top off to 40 gallons.

In other words I get about 500 miles on 30 gallons.

Did you fill up when the Light came on?
What was you DTE when you filled up?
How many gallons did it take to fill up?

 

I just got back from a 600 mile trip and got 22.5 hand calculated & 25.4 overhead. That was @ 75 & 1750 rpm's. I have 13,000 mile on the truck. In the city I get 16 -18 but depends if I can keep my foot out of it.

 

strang?? the sweet spot on the ho diesel starts at 1900-2100 rpm on my 06 i get 1900 rpm at 70mph. cruse on. i wonder why your so fast with 1750 rpm

 

Something doesn't match up with your numbers.

315 = 35 to 35.5
Auto = 3.73
OD in the 48re = .69 (IIRC)
75mph

1853rpms

22.5mpg?

 

Maybe he didn't correct his speedo?

 

I just have one question to all the MPG posters with larger/oversize tires.
How (if any) are the tire size differences being calculated.
If you put oversize tires on your truck and don`t change any calibration`s.
Your data for miles driven, MPH and MPG are erroneas.
I see numerous trucks with 315`s claiming 2xx.x MPG`s.
You gotta Lotta Splainin to due Lucy....

 

Mine was corrected to exactly 36.9" diameter tires which is what I have thanks to the Smarty!!!

 

My 315"s measure 33.4" I multiply my mileage by 1.08

 

I have a 06 megacab and went through the same thing I was wondering were my milage was this being my third Dodge "BEAST" the milage was horriable after taking it to the shop to get checked they tried to tell me to give 5000 mile to get broke in and I had 25000. Then they told me my Idel time was 33%of the time thus being the problem w/the milage. As a Const. Super. I am in and out of the truck and it does run alot but it never affected the millage on the others. I was all was avg 20-22 mpgs those were the good old days of the good fuel economy. I have talked to a couple of guys that have a standards and are getting 16-18mpgs so if you are looking I would say go with the manual trans.

As far as the mpg avg. console if you are driuving down the high way and continue to reset it every couple of min it will get to 33mpgs. I did it going to Houston that @#$@ thing is a waste of space in the console. Best thing to do is stick to the math to figure the milage.

sorry if it is so long this is one topic that gets me wound upif any one has any suggestiuons please let me know.

 

Then you'd be at 1942 rpms assuming you have the 48re.

 

When new, BFG 315s are roughly 10% (round number, actually 9.67%) larger than my stock tires, so without correction I will travel about 10% more miles than my odometer says and about 10% faster than my speedometer says.

Personally I just use my GPS for miles driven and the number on the fuel pump for gallons used and fill up each tank.

 

I have corrected my speedo with the superchips programmer. I used my GPS to verify miles & speed.