Hounddog

I can hit 18 by a little at 55 mph or less non towing of course.My 1998 1500 2wd 1500 slt 5.2 and my 2003 3500 get about the same mileage on hiway at 70 or so.Neither truck has every hit 18mpg at 70 plus or 70 for that matter.Now my 1985 Chevy Caprice with a 305 4bbl 4 speed auto and a 2.89 rear gear will hit 22.5 at 70 and no hills.It is more like 20 to 22.5 on every tank with a 100 miles per day with 96 being all interstate.But the other two NO WAY.

stevenknapp

Muzzy,

Good thoughts on the fuel. It's a factor, like driving style and all that.

I've seen too many posts by folks like Sittenbull or Houndog...where you read it and think, man those 600s are crap, then realize they've got older 555s!

I've got my fingers crossed for my truck.

Hounddog

My 1993 W250 4x4 auto 4.10 gears with a Banks intercooler,14mm turbo housing,3.5 exhaust with dyna flo muffler,stock fuel pump with 42 h.p. indu.injectors and a TCI torque convertor,stock tire size got a best of 17 at 70 with cruise on downhill or big uphills.Towing same load I pull now it mananged 11 to 11.5 with a max of 68 mph.Mainly on the flats(several trips out west towing.it didn't pull this load as easy or had anything in reserve.Around town 14 or so.I had it 6 years or so.speedo was dead on and I drove it most everday.This new one does a tad better and pulls LOTS harder and smoother.

sawood

Well, theories of heavy footing - head winds - bad fuel - etc.... I am sure these effect our driving MPG's, but the bottom line is - i have driven cross country and bought fuel all over, tried under 70 mph, then went to 80-85 and got same 13-14 mpg not matter what. Its the 3rd G's new cat converter that takes a another blast of fuel (3rd fuel injection in the series as mentioned in ealrier threads) to help burn the exhaust fumes completely. BTW i have the vibe at 74-79 mph/2000 rpm but i can push thru the feeling, its not that bad for me, sounds like drone but rearveiw mirror vibrates images behind me. I wish i could say i was getting that kind of mileage, thats why i bought it. Still love the truck but i dont see many posts stating their 600/325's are getting better than mine. If you are - send me the secret would ya? Tired of it all - jsut going to drive it and enjoy it. Much better than any gasser I ever have owned. Maybe DC will eventually get it right, hate being a test guinea pig with my money. The thing that really gets me is i knew of this and been following these threads for months and i didnt buy the 555...............ouch!!

2004.5 4x4 quad swb auto 3.73

toddbweaver

Would just like to let some people know that my fuel mileage for the first 4k is averaging about 18.5. I'm am a light foot and haven't pulled my trailer any distance to speak of yet. Had the engine test done and passed. Drive it every day to work and back. Only about 10% of my travel could be considered highway. Most of it is country road 35-55 mph. My truck is totally stock. 04.5 QC 4x4 LWB 6 speed with 245/70/17 tires. Hope this helps those who are afraid to buy a 325/600 for the mileage.
Since I have an ST I have hand calculated the mileage since I bought it.

stevenknapp

Its the 3rd G's new cat converter that takes a another blast of fuel (3rd fuel injection in the series as mentioned in ealrier threads) to help burn the exhaust fumes completely.

The 3rd G's include the previous 555HO motor which didn't have the cat and didn't have the third injection event. So are we talkin about 3rd gens or the 600?

I'm really starting to think this is just the 600 being new and people comparing above average trucks with below average. Threads like this one or this one, which seems to be all *555* owners, no cat, no 3rd event, talking about low mileage too.

Sawwood, are you towing, or just empty getting that sort of mileage?

sawood

Stevenknapp, I am not towing and that is empty readings of 13-14. And, i am talking about 600's, not 3rd G's, i guess - thought one was the same but ignorance has a way of creeping out. I am afraid to go to the dealership in Tucson cause every time i have in the past, the truck comes back slower than it went in. This truck at least has get up and gooooo! So tired of being threatened that if i dont buy the extended warranty that i will be on my own after 36K miles except for engine i guess. but this truck seems strong and i dont need to spend the money. Just get some decent fuel mileage was all i am lookin for.

With 2700 miles on it from driving cross country at varying speeds of 70-90mph, i still get 13-14 and in town i get the same. There is no real difference it seems btw city and highway mpg's.

If anyone gets a true fix to their mpg problem, plz email me direct with yoru solutions at sawood@aol.com as i will also wait to see what break-in brings me as well. Met a guy at the beach who had same truck and said he got best was 16.5 but i dont think he got much better than me driving to Mexico.

2004.5 600 4X4 Auto 3.73 QC 2500 Brite Silver Everythign but leather

stevenknapp

Did you see the thread about the possible computer flash upgrade that has helped some?

If you travel a lot pick a dealer that's along the way that has a good rep, Carson City or St Louis maybe? Call them and see if you need it.

Luke S

My wife just took a new 600/48re/dually/3.73 off the lot the other day and it is getting 14.0-15.5 empty. 10-12 pulling hard. It is getting a terible amount of black soot all over the bedside though. Don't know what is causing that, have to have the guys check that out?

Luke S

BTW, it has 2000 miles on it and was built in march.

smiller

While it's true that anecdotal evidence will usually be all over the place and yes, most everybody has complained about the mileage of most every vehicle ever made at one time or another... but there does seem to be a consistently higher number of compaints from 600 owners. There are many reasons why that message could be flawed (such as dissatisfied owners being more likely to post than satisfied owners, etc.) but it's hard to discount the sheer number of complaints dealing specifically with the 600. It does seem likely to me that the new ECU calibration has in fact negatively affected mileage to some extent, but I also believe that Cummins/DC will eventually fine-tune this problem away so I don't think we will be living with this forever. Emissions controls are kind of new to heavy diesels so there is a learning curve. Gas engines also took a big mileage hit when emission controls were introduced a few decades ago, but after many years of experience modern emission-controlled gas vehicles by and large get much better mileage than their counterparts of the past. I expect that the same will be true for diesels as the knowledge base grows. I thunk the future will be bright even if Cummins may have hit a little bump in the road with the 600.