Little-bit

I have a 2002 dodge 4X4 diesel with a 5 speed manual transmission. I hear of people getting 18 mpg with the same truck. The best I can get is 15mpg and that is running on the interstate and keeping the rpm’s slightly below 2K. I bought the truck used with 75K miles. It has 4:10 gears and 315-75-16 tires. I think that makes the gear ratio close to 3:77’s. The only upgrades on the truck are a 4” exhaust, KN filter and a 40hp Power Puc. I ran the truck 300 miles this weekend with the Power Puc unplugged. I averaged the same mpg. What’s the deal??

Buckshotmckee

I'd say get rid of the K&N drop in filter and factory airbox and install a BHAF. Do a search on BHAF (Big Honk'n Air Filter). I have pics in my gallery.

Bosshawg600

That does sound realy low. I run 4.10 gears and 35's with a 5sp and I got 19 mpg on the HW with a 40 MPH head wind. Is it burning a lot of fuel, ie lots of smoke? Could be a number of small things like even a fuel leak. I would listen close and look all around for something out of wack. I hope some other guys will chime in with some more help.

Andy505

That does sound a little low. The only time I got 15mpg was when I towed another 3/4 ton truck back from Iowa. I average between 17-19 in city and on the highway I get 20-22. You should definately be seeing better mileage than that.

kawi600

Hm, you guys are lucky.. Im getting 10mpg with my 4.10's in mostly city driving. Doing a long trip on the interstate boosts that to about 12mpg.
Im guessing the problems are between the transmission and the injector pump.
Could be injectors for all I know, but Id have to do DV's at the same time since my pump is a 160, and thats expensive.

Little-bit

The air filter is not a drop in. I am not sure of the manufacture but it has replaced the factory air box. The truck only smokes when switching gears.

bluedodge3500

I get 14-15 around town and 17-28 hwy keeping it under 70mph if i go over 14-15 then

Little-bit

Back to top. I need some help guys. Where do I start looking for better mileage?

billv45

Check for boost leaks. I found one in my quest for the MPG's. Of course I started out at 12 and now I'm all the way up to 14.4...
I used a 4" PVC with a valve stem stuck in tube that connects the filter box to the turbo to plug and pressurize the system. The intercooler boots are a good place to start checking.

Danderson

Try replacing the tires with next size down. You've got a lot of rolling resistance and weight to keep rolling.

CJ

Maybe a dumb question but when did last change your fuel filter and how often do you change it?
CJ

kawi600

Things that can cause fuel economy problems that Ive read in my searches:
Transmission (if you have good highway mileage and really bad city, maybe your torque convertor is bad)
Fuel pressure (get a gauge for the cab and look up spec for your year truck) Low pressure could be clogged filter or bad LP
Clogged air filter
Boost leaks (check the pipes and joints with soapy water and < 30psi compressed air)
Clogged injectors
Poor compression
Injector pump problems. Needs repair or recalibration?
Dragging brakes

with my truck Im down to looking for worn injectors and injector pump. I havent run a compression test but when I look into 370's Ill do that. I get the same mileage in TC lockup so its not that. Filters are new, boost is good, brakes have all been replaced, etc. Mass Diesel recommended I have my pump recalibrated but Im thinking the best bang for the buck is going with a reman 215 at 900$ instead of fixing my 160.

high country

ok first off bigger tires cover more ground so you may not be doing as bad as you think, after a 500 mile drive, according to the odo, you might find that you have gone quite a bit further.

having said that, when I bought my truck the mileage sucked, it was 14-17mpg and was not gonna do any better than that. I first changed all the fluids and filters.....nothing, added a pusher pump.....nothing, big line kit.....nothing, the superchips program....picked up to 17-19, then a van aaken......19-22, then an edge drag comp.....18-20. I should say that after the superchips I added injectors and never ran w/o one of the boxes so the injectors could have been the boost in mileage...who knows.

I also tried cleaning the IAT....nothing, new MAP sensor.......nothing. pretty much I was sure my inj pump must just be a bit retardedand I'd be buying a new one soon......50K miles later I think it might just be that my pump was a bit retarded but I "smartend it up" with the adv timing of the programmer and box combo. I have good mileage plenty of power and as of yet no problems.

Little-bit

I have been checking the mileage with a GPS. I know that the milage is of 8 tenths/10 miles. I just changed the fuel filter. This is my first diesel truck and I am not familiar with the boost test. I am learning as I go. All I know is the boost presure has something to do with the turbo output...Or I think it does.

volly818

Go to the dealer and have the fix your speedo with the right tire size. Should only cost $25 or so,may get lucky and not cost anything as I got. If you are going by the odometer your milage will be low due to the change in tires. your milage may not be as bad as you think.