I knew that would get your attention!! It's actually partially true though... that was the reading the overhead showed before I reset it.

Anyways, the truck was an '04.5 2500 SLT SRW CTD 600 4X4 QC LWB 6-SPD 3.73. On a half hour test drive with varying grades and speeds, even after resetting the overhead, it never showed lower than 20.5MPG. Given the fact that the overhead's numbers aren't always 100% accurate, this is still outstanding for a 600 right off the lot and is about 8 more mpg than I get with my 600.

Since I drove the truck the same route as I drive mine, and I applied the same driving habits, and taking into consideration that the manual should only account for 1-2 more mpg... I'd say that there is definitely something wrong with mine (early build dates, see sig). Could it be that this new one had the "miracle mileage flash" we've all been waiting for? It also sounded different... much smoother. Mine has developed a knock/cackle that I thought was typical for a diesel, but the new one didn't have it... could just be because I have some miles on mine tho. I think I'll go back to the dealer and have a look at the build dates and see if I can find a TSB sticker... would have done that today, but ran out of time.

I really wanted to buy it, but I think I'd take it in the shorts trading in what I have, being that it is so new and I owe so much on it. Might still be worth looking into though... my math says I'd save about $100 a month on fuel by switching trucks!

 

Hey BigRig,
My engine build date 12/19 and truck build date was 01/04! what mileage numbers are you getting?
Odie

 

Odie, my mileage is now going down with every tank... The truck started out in the mid 12's... The best I've ever seen was 15.25 and that only happened once. I was averaging 13-14 for a while, but recently it's been mid 12's again... just filled up tonight and I only got 11.77mpg out of the last tank (all time low for running w/no load). I don't know whats going on with it... starting to think fuel filter?? I've only got like 5300 miles on it, so that seems a bit premature, but who knows. I'm also switching fuel suppliers starting tonight to see if that makes a difference. When filling up at the station where I've been fueling since new, there is little or no foam when filling, but the place I filled up tonight was foaming like a laundromat! It took me about 15 extra minutes and what seemed like a hundred clicks to get the fuel to be visible in the neck. I'm new to diesels, so I have no idea what the foam is all about, and whether it's good to have more or less of it, but I'm thinking maybe it's like beer... once it's foamless, it's flat... and generally not as good???

What kind of numbers are you getting?

 

Friend has 49-- on his and his MPG is 11.? 4wd 4dr 3500 HD600. I cant belive thier getting such back milage.

 

OK, I understand that most of you think or may actually have a mpg problemm however how are you calculating your mpg's??
Is this city, highway, combined, or what you call city driving. I say this because real city driving is not reaching 45 mph for any long period of time and having a million stoplights. If you guys are getting on the highway at anytime then it's NOT city driving. you also have to take into concideration that you are running the A/C in the CITY and these trucks just hate having to try to run that thing at such low speeds without getting any airflow accross the cooler so it cuts in the cooling fan alot more, you probably noticed the difference in the sound of the engine when taking off from a stop light, sounds like a jet engine taking off. If all of this is the case then 11-13 mpg is normal for a 3.5 ton truck.
If yo are saying that you are getting that kind of mileage on the highway, sustained speeds in excess of 55mph then yes you are correct your mileage SUCKS
My city mileage has gone down since I've running the A/C full bore, I'm now only getting about 11.5 around town by the overhead, I do hve to wit until I fill it to check it becasue of the BAnks Six Gun.

 

bought my 600 4x4 auto 3.73 2 months age . built 3/04. i have never taken it on the highway although some of our roads are 65 mph. each tank has produced better milage-started at 14 and now 17.1. i have 1500 miles on the truck ,fill up when 1/2 empty and hand calculate. my overhead is around 2 mpg low

 

Biggrigg,
Diesel is extremely foamy. You might want to change the fuel filter. I usally get 17-18.5 mpg @ 65 all highway (hand calculated)
14-15 mpg town driving (summer beach traffic makes it drop lower, however that's bumper to bumper traffic). Several weeks ago I filled up at a brand new Exxon station ( I was the second diesel customer) So I thought the Diesel was new. It wasn't, it had been sitting for several months in the storage tank. ever since that fill up , i get 2mpg less. I'm going to change my fuel filter and it should jump the mpg back where it belongs.

 

Don't get too excited, if I reset my overhead driving down the road w/ the RPM's around 1400, the overhead will tell me I'm getting like 35 MPG. You got to give the over head a while to calculate and give you an accurate reading. Usually within 20 miles or so I am getting a pretty accurate reading. -Steve

 

I meant back up to my original mpg. My overhead computer is off by 1.5 mpg all highway and 2.0 mpg in town. 10k on the truck and the overhead computer has never been close to accurate.

 

I have never hand calculated my mileage doing only city driving but the overhead would show anywhere from the low 10s to the upper 12s when in town. My calculated mileage for combined mileage was usually low 14s to mid 15s. Highway driving was usually low to mid 15s. I now have 11000 miles on the truck and I am getting mid 16s to mid 17s combined and upper 17s to 18 highway. I have made one 660 mile tow with my truck pulling my travel trailer, approx. 10K lbs, and I calculated 9.9 on that trip. The tow was at 7000 miles and my mileage has improved since then. I do watch the overhead and it normally runs 1.5 to 2 MPG low.

Engine build date - 2/26/04
Truck build date - 3/04

 

My overhead is very accurate - usually within one or two-tenths of hand calculated - and I almost always use the same diesel pump, and fill until I can fill no more.

 

Wexman what kind of mileage are you getting with a 4.10 rear end???

 

I have 1500 miles on my truck, been getting 14.5 with no highway driving. Just did the first highway trip not exceeding 70 MPH, mostly 65 with the cruise on. Got 14.2 . One thing I noticed was the turbo constantlly sings. Wonder if there is some type of adjustment (wastegate???)
Reason I say that is I had a 7.3 F350 CC with the same gear (4.10's) and the only time the turbo made noise was under acceleration. That truck got 19 on the highway all day long.

 

On my 11-mile stop-and-stop commute, I average around 12, IF I keep my foot out of it. Highway mileage at 70-75 around 14, best I have ever seen was highway around 17.5 when I was in heavier, but steady traffic, and going around 55.

My 7.3 PSD got in the 15s on that same 11-mile commute, but that was a single rear wheel, lighter, 3:73 geared 6-speed, with 50 less hp, and 80 less lb-ft, so it's an apples-to-oranges comparison.

 

I have to agree with Scott (Wexman) regarding the mileage. Mine is right there with his.