I have an LLY 4" lift w\ 35" tires. I have had the Quad Box, and Edge Beta. No matter how I drive this thing, I cannot get more than 13.2 MPG combined. On the freeway 70-75MPH, the best it will due is 14.4. I realize that the DIC is wrong because of the tires, but even figuring in the tires it is bad.The truck has 4" exhaust, no cat, and intake. My Dad has a 325/600 Cummins w\ 35" tires and is getting 20+ MPG'S. Any ideas???

I have never even heard of a 600 Cummins get 20 mpg stockhttp://www.dieselplace.com/forum/smileys/Confused.gif.... My d-max has 285 tires, other than that it's stock. I get 15.5 mpg hand calculated. I have 800 miles on it and from what I understand I can expect to get 17-18 sometime in the future.

Any ideas???
Yeah take off the 35" tires and see what happens. You'd be surprised what a 35" tire will do the mileage, and in your case it looks like you underestimated the outcome.

Dodge getting 20mpg...now thats funny!Edited by: y2kboti

Koopdaddy,


I have the same setup on my truck 4" with 315/70/17's (35's) and have the same mileage problems. I'm really easy on the truck. Thought I could get better mileage the easier I went. I was wrong. Right now DIC says 13.4 and that's almost all country roads and freeway. With lift best I've gotten was 14.5. Best I got with original tires was mid 16's then went with the lift/tires and mileage went down the tube. I'm actually pretty confused. I'm aware bigger tires= more rotating mass but at speed (highway) bigger tires also= less rotation per mile= engine working less. Truck speedo never gets over 70mph on the freeway.


I feel your pain buddy.http://www.dieselplace.com/forum/smileys/Cry.gif


Rich.

It still takes the same amount of energy to propel the same mass at the same velocity. Discounting any increases in engine efficiency (probably minimal karnot differential anyway) the increase in rotational mass should have a significant affect on your mileage, not to mention the additional friction loss you are incurring as a result of the larger contact patch of the tire on the road.


Any thoughts?


Dennis

for the most part you will lose mileage with a lift and bigger tires, its just a given - i have the rancho 4" with 305's and get just under 15 hand calculated, on freeway for long periods will get 18. All in all, not bad and i knew i would get less with a lift but its still better than my last gasser http://www.dieselplace.com/forum/smileys/Big Smile.gif http://www.dieselplace.com/forum/smileys/Big Smile.gif

I bet everyone would get better mpg if we all drove around in the middle of the tourque curve and used the throttle a little less, I'm not an automotive wizzard by a long shot, but I was always taught that it takes energy to overcome gravity, weight, friction, and I would bet most of the guys here with experience calculating all the variables in a particular truck, would come up with a pretty good estimate of mpg if THEY were driving your truck, but like the man said when I tried to take back a broke video camera, "hail boy, I caint see everything goin on out there where that thangs been"