MARKY MARK

I bought my truck used in November. Shortly after, I put an AFE filter in the stock box. I am not really sure what my mpg's were before the AFE, but since I put it in I am getting 11.5 to 12.5 mpg's city & 14 highway. Could it be the MAP sensor, the AIT sensor or the lift pump. I will be installing fuel pressure gauge in a few weeks so I can't tell if lift pump is the problem. Any ideas?

phox_mulder

That sounds about right.<br>The combination of the 4.10 gears and winter fuel would put you in that range.<br><br>My 2002 with 3.55 gears maxes out at 16, pure highway mileage, winter fuel.<br>Normally averages around 13, with winter fuel.<br><br>Last summer I was averaging 16, but engine wasn't and isn't broken in yet.<br><br>I'm assuming that Eureka is far enough north you'd see the winter blend.<br><br>phox

MARKY MARK

I asked the local fuel distributor(they control the whole market here in Eureka) &amp; he said they do not use a winter fuel because it doesn't get cold enough here. Only gets into the lower 30's &amp; 40's in the night/morning &amp; 55 to 65 during the day.

AlK

As a first gen truck owner if my truck would get that kind of mileage I would say that &quot;sucks&quot;. Have you changed the fuel filter and I believe, that I read somewhere, that on the second gen trucks there is some kind of a screen on the lift pump that can be cleaned (if I am wrong someone please correct me).<br>---<br>Al

Ballbearing

Mark, My truck is essential the same as yours except I have a 6 speed. I feel your pain about the fuel mileage. Diesel is $1.66 US here.<br><br>I filled up yesterday and calculated mileage was 14.63. The computer showed 13.8 MPG.<br><br>This is combined driving. Usually 50 city/50 highway (60 MPH)<br>Mileage has been steadily going down this winter. I usually average 16 MPG in the summer. I haven't been able to get any better than that. Mine isn't broken in either as I have 7400 miles right now.<br><br>I've been reading numerous posts about excellent mileage and I'm getting somewhat upset. My 99 F350 Powerstroke got 17 MPG summer and 15 in the winter. That was way before break-in. I'm losing faith in this Cummins.<br><br>I've checked my lift pump pressure and it is at 15 PSI idle. Mark, If you're not having any other issues then I would assume that you are also OK. As far as the other items mentioned I don't know.<br><br>If this doesn't improve I may have to get a diesel Jetta (40 MPG) and rent a truck when I need something moved.

StakeMan

I get 17.5 mpg running around Denver. My last trip through the mountains and back was 23 mpg. I have never had the truck on flat ground to see what it would do.

My point is that my truck has 4.10's and an auto tranny and I seem to get good fuel mileage. If I was you I would check the IAT and MAP sensors. Not just clean. The sensors are not expensive to replace.

Also, if you changed tire size, are you allowing for the differnce in your calculations?

MARKY MARK

Is the best place to get the sensors at the dealer or parts store? Are they easy to change out? Yes, I did calculate in the taller tires I have on right now. I have 265's now, so it wasn't much of a difference.

StakeMan

I got mine from cummins. They cost about $30 each.

The IAT is in bad spot and requires a 13/16 deep socket.
MAP is 1 1/4 deep. Cummins may have changed the socket size though.

BAD HABIT

Mark, I have the same problem. 14.5 MPH Being my best ever. I have already changed the IAT senser. TST powermax co. has MAP senser for $50. Dealer has it for $97. Will be replacing MAP when it gets here. My fuel pressure is up, exhuast is opened,&amp; BHAF. Mileage s#*ks. Good luck.

Shovelhead

I find that if I keep it at close to 2000rpm on the highway, I get get decent milage (for 4:10 gears).
Running above 2k rpm on the highway, and stop and go in town really blows my milage all to heck.
If I watch the boost gauge and try to drive without generating a lot of boost, I get better milage, but Geeeeeze it's boooooooring. :

DarrellB

With 4:10's, a 4x4, with a 5spd, and pushing a set of 33x12.50's I can manage 16.5mpg with winter blend and a wopping 21.5 with good fuel on an open highway. 8)<br><br> My truck also runs very low EGT's, with my PM2 and DD3's I can't get it above 1,300* in a hard pull unloaded. That's with the stock HX-35 turbo as well. <br><br>I think it has more to do with the computer programming than the gears or fuel, but what do I know? :-[<br><br>DB<br><br>

katoiler

My best to date is 15.2 mpg have 9000 miles on it now, but it stays around 14.4 mpg combined.tried on one trip to keep at 2000 rpm,but the milage was the same.the only thing that changed was my foot was sore from not resting on the right foot pad ;D

geer

I have a 2002 DRW 6 Speed. The best I get unloaded is 14. Loaded at 7000lbs(trailer 5200,3 sleds 1800) I get 10. I average around town about 11.