rbox

Ok. I hate to start another fuel mileage thread but surely someone can help me figure out my fuel mileage problem.. It seemed to get better mileage before the dealer did the injectors. And it smoked then too. Now I have almost no smoke with the new injectors but the fuel mileage fell. I was expecting an increase in mileage.

265/70r17 Goodyears 80psi front, 65psi rear.
4.10 gear.
Did APPS reset.
Cat, silencer, intake baffles gone.
Boost leak that is only audible at higher boost levels.
#2 diesel.
Otherwise bone stock.

I buy quality fuel, most of the time I use Stanadyne performance formula.

MPG:
City+Oldman driving: 11
City+Normal driving: 9
Highway+Oldman driving: 16
Highway+Normal driving: 14

Watching the overhead, when I hit the hills it just drops like a rock. I thought diesels were suppose to handle loads without losing too much mpg? Mine just starts sucking fuel at the slightest hint of an incline...

I had fuel leak problems after the injector replacement. Could I still have a fuel leak? What is a surefire way to tell?

I have a travel trailer I may be pulling some this spring, but I'm afraid that it will drag it down to 5mpg with the way it sucks fuel at the hint of a load. In which case it would not be worth it to run a diesel.

When I bought the truck it had an Edge J/A set to power level 3. I got just over 20mpg on the trip home, and that included some stops along the way. The Edge has been removed.

Is it realistic to expect 14mpg city and 18mpg highway (empty) from this truck?

Thanks for any help!

92'1stGen

First, are these figures based on the overhead?, if so don't go by that, the OH's are never right. Second, if they are hand calc'd, something doesn't add up, they shouldn't be that low. If you say you had fuel leak problem's after the injectors were replaced, what did you do to fix that? If nothing was done then there's no reason you couldn't still have a fuel leak, but you should be able to notice it pretty well, diesel has a strong scent.

As far as realistic mpg, I would say 14 - 15 city is very realistic from one of these truck's. I can do 15 regularly in 60 city/40 highway driving and I'm even less aerodynamic than you are. I don't drive like grandpa, but I don't hot rod it either. Keep the RPM's below 2k on acceleration, it make's a big difference.

rbox

I am going by the overhead most of the time but I have hand checked it as well. My overhead computer and hand calc are pretty close, less than 1mpg off.

My dad has a 1/2 ton with a hemi and (empty) his truck makes mine feel gutless. Mine has no pep. And he gets better fuel mileage. It's starting to suck driving this thing.

SOhappy

Air filter/intake?

Have you cleaned your IAT and CP sensors lately?

rbox

Cleaned both IAT sensors last weekend. They weren't that bad anyway. The dealer supposedly fixed the fuel leak after they did the injectors.

What is the CP sensor?

SOhappy

Sorry. Crank position sensor, on the front of the engine behind the tone ring. Not that I've tried it, but I read on here that cleaning/replacing the CPS after 50k miles will improve mpgs.

Ace

The overheads are more accurate than most people seem to give them credit for. You just have to remember they calculate more than two things (gallons and miles) to come up with the number they display.

rbox

I will check the CP sensor. I just can't help but think there is something bigger that is amiss. I wonder if fuel is seeping out onto the engine from an injector line...

MiB

Where is these sensors located?

snoyes

If you have a leak, you probably be able to tell by a puddle under the truck after idling it, or an overpowering smell of diesel in the engine. My long term average in my truck is about 15 MPG, so it seems you are in the ballpark, though I have 3.73s and you have 4.10s. If you are using the overhead and are 1 MPG off in the negative direction, your numbers for normal driving is 15 and highway is 17, which has to put you close to others when it comes to MPG with 4.10s. If you were pulling the numbers with the programmer on from the overhead, you would be surprised that programmers tend to change the MPG reading on the overheads, making your mileage "seem" that it gets better. Also, have you calibrated your speedo to a GPS? I find many vehicles I've been in are off, and that actually effects MPG people think they are getting.

rbox

Thanks for the input. I will take all of this into consideration. Maybe clean the MAP sensor. I am going to hook up to my dad's travel trailer soon and we will see what it gets hand-calc.

DBLR

Hand Calculating your fuel mileage is the only true way to know what your mpg really is.

Spooler

Drove my truck last week to and from work, since i lost my company truck and my daily driver is getting new floorboards. I like to fell over. I got 19Mpg hand calculated. RPM's set at 2200 RPM at 73 MPH on the interstate 95% of the time. Excellent.


So much for the overhead, it read 19.7 MPG average.

TAS05CTD610

One thing to account for is speed. Yes I know some people say hey, I can get 22 out of my 3rd gen, when another is only getting 14. Well the 22 guy is driving at 55 on flat land, and the other guy is in the mountains doing 80, so not only calculate your MPG, but also factor in speed, that helps a lot.

Also with 4.10's, an auto tranny and 265 tires you have to be turning some high RPMS. With my 3.73's and auto, and 265 tires, I'm at 2100rpm at around 75mph, so you are most likely at 2200-2300 rpm. And from what I have read, anything above 2,000 rpm in these trucks, you start to burn a lot more fuel. So the possibility of a 285 tire, might actually help with your low gearing.

And as others suggested, check everything, fuel filter, air filter, all of these will contribute to bad millage, but the worst millage I ever got was pulling 7K pounds and I was still at 13pmg in the mountains (at 75mph) Again slower speeds, better mpg. My best ever in my 3rd gen (35,000 miles) was 21.9, it was because the roads were snowy and I was around 50mph.

Also towing, you problably won't see your numbers change much, again since your 4.10 gears, towing you will have a easier time than somebody with lower gears.

And you mentioned a boost leak, find that sucker and fix it, any air not in there is unburnt fuel (wasted) so fix that too.

SOhappy

IATs on the air intake tube by the air filter and on the intake "manifold", sort of behind the grid heater a few inches (for lack of a better description).

CPS on behind the tone ring on front of engine.

BTW, where in Sweden are you? My wife's from Malmö, might be going there this summer.