I'm thinking an increase in hp & torque have eaten into the fuel economy a little.........anyone else agree ?
Greg

 

I thought I read a post by someone who had done dyno runs comparing the 555 to the 600 and they concluded that the hp and torque increase never actually showed up.

 

The only thing I know about horsepower and torque eating away at our mileage, is there are many 2nd gen trucks making well over 400 RWHP that are getting better fuel economy than most of our stock 3rd gen engines. They did not have to meet the same epa specs when their fuel injection system was speced.
Jason

 

I read somewhere that it could be a bad Air intake temp senser reading out of spec. not sure how to check this, but the only fix is a new senser.

Maybe someone could check this out and let us know. I would but my truck is on order and maybe 8 or more weeks away.

 

The only people that are posting mileage figures on these boards are the ones getting bad mileage, so everyone automatically thinks the 600's are a real turd of a motor that get's horrible mileage...NOT TRUE!!! My 600 gets 17 in the city and 21 on the highway. You can't ask for much more than that out of a 3500 series heavy duty diesel truck weighing in at almost 4 tons. My boss has a 97 4x4 quad Dually with auto and 4.10's, he gets 17 on the highway. Not long ago I read about a guy complaining about his 04½ 4x4 quad dually with auto and 4.10's only getting 14 in city and 17 on the highway, what the hell do you expect??? I don't believe anybody telling me that they get 28 mpg or some unrealistic figure like that...it's just not possible. When someone tells me a figure like that, I question their mathematical skills. I do understand that some are getting terrible mileage, around 12 and 14 mpg on the highway...that is unacceptable in the least, and would say that there is something wrong with their truck somewhere. But this has happened with every series of diesels in every brand of truck. There are people with 03 555's that are getting crappy mileage. I'm just sick and tired of everybody bashing the 600 on mpg issues. The vast majority are getting mileage that are commensurate with driving habits, mostly above 17 on the highway. The single biggest factor in mpg's are how you drive it. Also, give them a chance to break in...I just finished driving the Alaska highway from Wisconsin pulling a 10k 5er. Overall was just a shade under 12 mpg over 3500 miles. Since then my highway mpg's have jumped from 17 to 21. Sorry for being so long, but this subject is getting ridiculous.

 

There are people with 03 555's that are getting crappy mileage.

Actually, I've been following this for some time. There are people with all generations of Cummins motors getting bad mileage. Here and there, there have been a few.

 

I now have 10,000 miles on my 600, but w/o any loads and just hills to climb for stress. 70% of my driving is from 70-75 mph and the remaining is city. After the fist few thousand miles I'd get an average of 17.3 mpg (hand calc) and it gone unchanged from that time. Now that I'm running the A/C fulltime my average has dropped about 0.5 mpg. If I could keep my hi-way speed at 65-69 the truck gets about 21 mpg. Although, I was hoping for an all around average of 20 mpg or more at this point. Maybe my expectations are too high? We'll see what the next 10,000 renders for mpg.

 

I own an 03 555. I just completed a cross country trip and had a chance to check my fuel mileage, all hand calculated with the fuel tank filled to the rim before and after. Freeway driving only, no load, only the driver: 469.6 miles @ 16.321 Gals = 28.77 MPG.

Who are you to be going around accusing others who report high MPG of being incompetent or dishonest?

I don't see 600 owners "bashing" the MPG issue. I see them sharing their MPG observations and some expressing their concerns. I for one am glad to see this information come out so that we can all be aware.

IMHO you're really starting to sound like one of those really defensive characters from TheDieselStop web site.

 

Hey sorry to make you upset, I just wanted to find out whats been going on with the new gen's. No bashing here either.

 

Bert&holli,
Ever wonder if all of this "bashing" has done some good? Check out all the newer build date 600's...they are getting about 3mpg better. Might not be much to you but that is over 100 miles per tank and would definetly lower my "monthly cost" to operate this beast. I paid thirty-something like everybody else and don't like the mileage I am getting....13MPG

 

Bert&Holli; You are fortunate to get such great mileage. My hand calculated mileage is 14.5 city with last tank. Last March my mileage was averaging 11 due to cold weather and a new truck. Since I am here in Fairbanks I have not really had a chance to get a good highway mileage check and will not ever get to 21 MPG untill I get on a straight and level highway in the lower 48 (that wont happen soon). I can tell you from my trip up here when I bought the truck new and towing a 24' inboard jet boat the best I got from Spokane to here was 11. All said and done I am a happy camper I get 2MPG better than my 02 Ford PSD, the engine doesnt stink and I have tons more power. I wish I got better but heh at least I am buying diesel at 20 cents a gallon cheaper than gas. If you notice some of the members who are reporting 28 are driving 2wd trucks and probably do not have alot of hills and marginal weather conditions. Bottom line is driving habits and conditions have the biggest impact on mileage.

 

dwhite,

I'm not so sure about that. Mine has an engine build date of 3/10/04 and I got a disappointing 12.6 city the first tank (assuming the dealer had filled it all the way). I took it out on the fwy for about 40 miles and the overhead was reading 17 and change but that came right back down into the 12s when I got back into stop/go stuff. I still only have about 500mi so I'm not panicking (yet). My only reference for comparison are the other posters on this board and my own experience with my 00 PSD which did about 17-18 city and better than 20 hwy - but it was a lighter 2wd truck and I got it with 35k on the clock.

Neil

 

Hey Jonesboro...if your getting almost 29 mpg (if I had a yellow BS flag, I'd throw it right now) you had better call Cummins and let them examine your engine and let us know what's different about yours. I don't care if you have a 2 wheel drive with the jet stream pushing you down hill, 29mpg isn't going to happen. You ask who I am to be accusing people who report such unrealistic figures?? Well, as a person who has been reading these message boards for years, have NEVER seen anybody claim to get that high of mpg. Are you sure your driving a full size truck or do you have that Cummins loaded into a golf cart, then I could see some pretty good mileage coming out of it. Frankly, your the only one to claim a number like that, if it's true, more power to you and congratulations on your one in a million truck. Furthermore, I'm not buying the whole build date thing either. My engine was produced on the 2nd of March, my Fathers engine made on 7 January. I get 2 mpg better than his, but I attribute that to mine having 5k more miles with over 3k towing pretty heavy. Really seems I hurt some feelings with my little note, I'm not out to do that, I just calls em as I sees em. Flame On

 

Maybe he is. He didn't say what MPH he is driving at..

Great Mileage at 55MPH.

Merrick

 

Lets bring this down a notch and keep it friendly