I thought I was happy..........bad mpg

[GAllen]

I hate to bring this up, but is a 4 mpg variation between hand calculated and overhead mpg normal? Overhead reads 19mpg and by hand is 14. 79mpg. Do I need some kind of repair or flash?

 

[MMeier]

Sounds about right... unfortunately.

 

[rjohnson916]

I've never hand calculated more than 1/10 differance from the overhead. But I've really only done this on long trips when I've been on the open highway 99% of the time.



-Ryan

 

[2Gen3Gen]

There is a TSB for the 04. 5 but Im not sure about the 05. (it may apply to early 05's) As for the mileage, I, myself, would leave the overhead alone. At least you will look at it after paying $3 or more a gallon and think, aaaaaahhhh, at leats Im getting almost 20 mpg! Sadly enough, these 3rd gen CTD's don't get what we did with the 1st and 2nd gen 12 valve trucks and guys that post the inflated 20+ mpg figures here are just dreamers.

The TSB that you would be asking the dealer about is the one for the white smoke at start up and the mileage. (note, some dealers will NOT do the flash unless you claim to have a white smoke cold start) It could help with about 1/2 of a mile per gallon, but I wouldn't get your hopes up.

 

[DavidBurt]

GAllen thats about right mine reads about 2. 5 mpg off. So if it says 19. 0 wich it usually does I'm really getting 16. 5 or so. But that 19. 0 sure looks good.

Dave

 

[klenger]

Have you done any fueling mods. If so, the overhead will read too high. My truck is stock and the overhead usually reads with a few tenths of calculated.

 

[DieselFiend]

Gallen, I'm having the same problem you're having. I'm getting lousy MPG so I'll be taking mine in to the dealer for the "white smoke on startup" TSB reflash. I feel your pain. I had an 02 with an EZ that easily got over 20 on the highway then I switch to this thing and amazingly my MPG drops a hole in my wallett. I'm very disapointed.

Also, my overhead was accurate before I put the edge J/A in. Now it reads really high and I'm getting worse MPG. Thinking about removing it.

 

[Turbo1Ton]

guys that post the inflated 20+ mpg figures here are just dreamers.

Well, I would have believed you about that a few weeks ago. I drove to Atlanta yesterday and got a hand calculated 20. 7mpg. I typically get about 18mpg or so with mixed city/highway driving.



Jeff



Edit: Sorry, forgot to say my overhead is about 1mpg high.

 

[GAllen]

Have you done any fueling mods. If so, the overhead will read too high. My truck is stock and the overhead usually reads with a few tenths of calculated.

No mods, this thing is bone stock.

 

[GECCO]

Interesting... . as my sig says, I have an 05 with J/A that has about 12,000 miles on it. I do about 50/50 city and highway (70-75 mph) and have been getting 16. 0 - 16. 5. I run the J/A on level 1/1 99. 99% of the time. My hand calc versus the overhead have never been off by more than . 1 mpg.



I'm due for an oil change and will switch to full synthetic, but I'm waiting for the new Mobil 1 Turbo Diesel 5w-40 to hit the shelves. I'm curious to see what (if any) improvement that yields. Don't get me wrong, the synth is worth it IMO even if the mileage doesn't improve, but any improvement would be great.

 

[Moose]

Stock my truck was getting in the neighborhood of 17-18 mpg mixed city and highway... On all highway I was seeing around 19-20 if I kept it at 67 mph... With the mods I have below. . I have been seeing 19-20 mixed driving and 21-22 straight highway at 67...



Moose

 

[Prairie Dog]

Either I'm another "dreamer" or maybe the 03's just seem to get better mileage.

I've gotten as much as 24. 7 cruising at 55-60 but normally I see around 20 with mixed driving. Towing my 7000lb TT at 60 I've gotten 17.

Oh, and my over-head is usually 1 to 2 MPG higher than hand calculations.



Scotty

 

[MCummings]

My Dad's overhead is generally 1MPG low.



He gets 18. 5MPG at 65MPH w/cruise and no a/c.



My truck, same situations, gets 19. 5. . Oo.





Both Handcalc, same day, following each other with minimum 3 second gap to keep from "drafting"





Merrick

 

[Dieselnerd]

Are you resetting the overhead when you refuel? If you don't reset it from time to time the error gets larger. I reset mine whenever I refuel and it's very close to hand calculated.

 

[Prairie Dog]

I reset mine every tank.

 

[Jack in Alaska]

Just made my 1st short road trip with my new to me 2004. 5 all stock... . yet. Had it re-flashed last week.

The overhead gave me 16. 9 at 60 mph using No. 1 diesel at 7 F. Will calculate it when getting back home.

 

[GAllen]

Are you resetting the overhead when you refuel? If you don't reset it from time to time the error gets larger. I reset mine whenever I refuel and it's very close to hand calculated.

I have been resetting it lately during fill ups, the most recent last night. Drove to work today 30 miles with no traffic and home in bumper to bumper (90 minutes!) and the overhead is reading 20. 5 mpg. I know I don't belive that. I'll have to refill sometime next week and I'll check it again.

 

[Turbo1Ton]

My tank that came in at 20. 7mpg was pretty much a steady 70mph from Memphis to ATL. The overhead was reset right after the fillup.



I usually reset the overhead at least every other tank, if not each tank.



Jeff

 

[mikeberry]

I wonder how much the poor tank vent has to do with everyones skewed numbers? If you install the better tank vent you gain 3-4 gal. capacity right? Are guys sometimes getting more fuel in and sometimes less, due to the funky air gap in a stock tank. This of course would account for a large swing in calculated mpg, and a large gap between calc and overhead.



Sooo those of you that have done the vent mod, pipe up and tell us what your getting since you now have consistant fill-ups!

 

[MMeier]

I wonder how much the poor tank vent has to do with everyones skewed numbers? If you install the better tank vent you gain 3-4 gal. capacity right?

Wrong, all it does is allow to fill up faster, it does nothing for tank capacity. I've put over 41 gallons on mine on several occasions before I did the vent mod, took quite a while but you can fill it right to the brim if you have enough patience!