06 Megacab, 5.9L, 6'' Superlift, 325/65 R18, Nitto Terra Grappler allterains, all stock engine except muffler has been removed by previous owner. Overhead console reads anywhere from 14.7 to 17.8 mpg. Fill up and milage calculations come out to 11.8 mpg....last fill up example: 24.12 gallons / 286.7 miles...I should be getting better than that shouldn't I...

 

Was the odometer recalibrated for your tires?

 

Not that I know of. But when driving I go 5mph under (on the odometer) the posted speed limit. I do have a superchips programmer on order and it should be arriving today. This will calibrate the for the bigger tires..aslo do you know if the 325/65 R18 is = to a 35'' tire?

 

it shoots you to about 13mpg if the speedo hasnt been corrected. Thats still low, but if you're doing a lot of starting and stopping its probably about right. Diesel engines are good but they're not magic.

 

tire height should be width x (ratio/100) x .03937 x 2 + rim size, I think? If I did that right, that would give a height of 30"?

I was thinking they were taller than that, and your truck could have actually put on significantly more miles than the odometer says, and mess up the fuel economy calculation.

 

No, you want to take 325 / 25.4 to get it in centimeters, then multiply by .65 for the side wall height. multiply that times 2 for 2 side walls and add 18 for the rim diameter. 34.6"

 

I just purchased the truck three weeks ago. The dealer that I bought the truck from puts the lift kits on and they sell them that way. So the lift kit & tires and wheels are brand new. I have 36,7XX mile on it now. I have used a tape measure and the tape shows just under 35'' tall but the tire is flat on the bottom due to the weight of the truck.... I'll take 13 mpg....the Ford V10 I had was getting 9 to 10 best in stock form and not near the pulling power...

 

I had asked around and some friends that have 5.9 diesels to see what kind of fuel mileage they were getting and they claim 16 to 20. One has 35'' BFG's no lift, stock wheels, performance chip. The other has a 4''' lift, 35'' BFG's, all stock....One of the reasons behind going with Dodge was the fuel mileage people were claiming....

 

That could depend on what years theirs is and where they drive. There could be as much as a 3 or 4 mpg difference between city and highway. the 03's and older get much better fuel economy. I have an '06 like yours. extremes unloaded are 16 town and 21 highway on 32-33" tires.

 

Thanks. I kind of thought I'd messed up somewhere.

MPG wise, I had an 03 SRW 3500 w/3.73 and stick, totally stock, and it could do over 21mpg if you were doing 55 most of the time.

My 06 is 3.73 dually stick, and I might see 18 or 19 if I'm lucky. In the winter where it gets driven a short distance from work and back, and idles while windows are scraped, I could get as low as 13.

Odometer is likely off a bit with 34.6" tires, so your actual mpg would be higher.

 

6" lift will cost you mileage all by itself and until you get your odometer recalibrated for the larger tires, you won't know for sure what your real mileage is. There are also many other things that affect mileage such as terrain, driver habits, wind direction and speed, tire pressure, etc.

 

I get about the same mileage as you do - around 12 in town. The computer hasn't been adjusted for the tire size, and the drivetrain is completely stock except for a K&N drop in filter. I do most of my driving in town also.

 

i get about 12 to 14 around town out of mine

 

Most of my driving is to and from work. 1 mile (25mph) to freeway with 3 stops to get to the freeway. Up to 65mph on freeway for 17 miles. 4 miles, 7 more stops (35mph). 22 miles one way to work... So I would think my mileage calculations should be up around 17mpg average...?????

 

You'll learn to sort through all the nonsense MPG claims.

A 6" lift with 35" tires eats your mileage. More wind resistance with the lift,and rolling resistance with the taller more aggressive tread.

I lost 3 mpg going to a 33.5" Toyo M/T. I average between 15-16 on the highway where I was about 18-19 stock. It wouldn't shock me at all to lose another 3 mpg if I was to lift my truck and put tires another 1.5" taller under it.

Last year there was a line up of guys wanting to take their lift off because diesel at $5 per gallon was killing them.