kkime

I have a 06 Dodge 2500 mega cab, has a 2in body lift and 315/70/17 All Terrain Tires, Ranch Hand bumpers front and rear. Engine is all stock. Purchase it used with 48k miles on it in Sept 09 seems to have different exhaust with no cat but looks like 2 mufflers towards the rear. Now has 54k miles and has always gotten poor mileage with me driven easy or normal, like 10.5- 11.0 city and 14-16 hwy tops. Just made 650 mile round trip this weekend and burned 1 1/2 tank of diesel and before trip fuel filter was changed, oil change with Rotella 15w40, air filter replaced with factory from Cummins, I never went over 72 mph and not over 1900 rpms ever on the trip on hwy. and hand calculated 14.5 mpg with first fill up. Also been using Power Service all winter and just tried Lucas on this trip and nothing seems to help. Truck runs fine and no smoke, no codes. Does anyone know what might be the issue, all my friends drive similar trucks same year and engine and get 16-17 city and 19-21 hwy?

tesla440

Check to make sure that your speedometer is calabrated for your tire size. More than likely you're getting that type of mileage based upon what you said.

Having that large of a tire on will hurt your mileage at take offs & being up in the air will hurt your crusing mileage.

I have slightly smaller tires than you, I get about 16-18 city/urban and about 17-22 hwy (depending on load). But I have free flowing intake/exhaust + a mild chip.

kkime

My speedometer is right on, I have checked it with two different GPS units and it is dead on per the GPS speed and by one of the radar post they set up on the hwy that shows your speed it was within 1 mph on the radar over this weekend when I passed one of those. I have talked with others that have bigger or same size tires and have lifts and dont get as bad of mpg as I do.

bigdave

That is usually what I get with my truck, and there isn't anything wrong with mine except that it has 4.10 gears, which probably aren't that great for mileage, but I wouldn't have anything else I guess. The two muffler deal throws me a little though. Never heard of that.

megacabdad

Megacabs came from the factory with a muffler and then a resonator over the rear axle. The muffler is the heavy and restrictive part of the exhaust system.

Your mileage isn't too bad, especially if you have been running winter blend fuel, which is a mix of #1 and #2 that will result in less mpg than straight #2.

A lift, heavy bumpers, and noticeably taller than stock tires will contribute to more rolling mass which equals less mpg, no matter how you look at it.

A Smarty Jr. or similar programmer with some added timing may help you a little, but will most certainly make your truck more fun to drive if you've been thinking about going that route.

idlewildranch

i have been getting 26 hwyy and 22 town,i have 315s on mt 17" wheels, i was getting 14 and 15 when pulling my small tt fifth wheel 22' before i changed my lift pump,it seems since i changed the lp ive been getting better milage and more power, i dont know why but at theprice of fuel now,im lovin it. maybe try that,,i used a fass lp and installed it myself. wasnt hard and 2 hrs. the local shop wanted over 800 bucks to do it, i did put a screw on fuel filter on before the lp. i just figured i had it laying around i might as well use it.now i have the stock one and this new one,hopefully the fuel willbe clean before it gets to the injection pump.

kkime

I have been looking for a reasonable programmer that might help me out a little bit. I actually tried the new bully dog e3 economy prog. and didnt notice any diff, so I returned it, and I am still looking, all I hear about are Smarty's but cant afford one of those right now. And not sure if that would help me out enought to justify the cost? I did take my truck to the dealer 2 months ago and they tried to trap me into the contaminated fuel scam, and then told me I had weak pressure from the lift pump causing the truck to run rich. I just didnt understand why if it's weak pressure why is it sending more fuel? So I didnt want to believe anything they told me and left. So maybe I should change the lift pump and go from there before buying a programmer...

tesla440

By the discription that you said, I would definately try a new lift pump. & you are right, low lp will cause you to have to use your right foot more to get up to speed, not dumping in more fuel. The stealship it kinda right you need to burn more fuel to get up to speed, & keep speed, but its cause by lower injection pressure retarding the timing.

kkime

I am going to replace the lift pump and hope all is well after that...

Bigiron

The lift and the big tires are costing you mileage (air drag and rolling friction). I haven't seen many people reporting improvements in mileage with a chip, but I have read many people reporting the opposite. As reported above, Winter fuel drops your mileage a bit too.

kkime

Well changed the lift pump out today and so far everything seems to be better already. My digital fuel pressure gauge that I had just installed a month ago and it never seem to work right because it was reading 0 all the time, well now it reads 7 and 8 psi at idle so it must of been right and I must of not had any pressure at all so I think the mileage will do nothing but improve from here on out. My overhead which is always off by 3-4 has never read more than 19 on hwy and on my trip back home after changing the pump it read 22mpg so already showing some improvement, so realistic prob was getting 19 hwy which makes me happy since I was getting 14.5 hwy before... also is 7 psi normal psi for my truck?