I am new to DTR but have been checking it out for a few weeks now. I just traded my 04 with auto for a new 06 with 6 speed. I was very happy with the 04, I just thought I needed the standard tranny for some of the towing I do. My problem is I used to get 22 mpg empty with the 04 and now I'm lucky if I get 15-16. The dealership I bought it from said I would get better milage with the 6 sp. WRONG. I am very dissapointed. Can any of you guys steer me in the direction of better fuel economy? Thanks

 

It needs to break in, be patient.

 

Welcome to the DTR! How many miles were on your 04? You know these Cummins need some miles on them for them to loosen up, before they start getting some decent fuel mileage. I'm guessing that those 315s aren't helping you out to much. Have had your speedo re-calibrated for the larger tires. Is this hand calculated mileage or overhead?

Tye

 

are you sure you got the 3.73's like you wanted? might have to re read your window sticker, I am not sure if they spend the money on the sticker in the glove box that says the rear ratio.

 

Arco. No amount of break in is going to help with a 2300rpm or so 65mph or whatever it is geared for. They dropped the 4.1 axle so they geared all the new G56$%&* extra high and used the 3.73. Your only solution is a gear splitter like a US Gear or other that gives you an overdrive between the tranny and the transfercase (if you have one) This will give you 20% less rpms or so. You could go with larger diameter tires which a lot of folks do. Or you could join the pokey lane and drive 55mph all the time. ks

 

Anyone else think that the break in period is super long?

Might be my imagination, but I really noticed an increase after about 40K miles?

 

your dealership was full of crap IMO. there is no way there are trucks getting better than 22mpg with the new 325/610 powerplant.

now was that old 22 all the time kind of number on winter fuel etc. or was that you best number ever. Did the truck get that good from day 1? usually they break in a little.

I don't know how often you calculated you milage? I just have a hard time imagining you were get 22mph hand calcutlated around town in your 04 every time.

I am at 24k on my 04.5 and the milage has come up some from new that is for sure but even on stock tires I would have have a hard time hitting 20mpg unless It was 100% freeway. it is wierd though I wish I would have paid more attention to the overhead during test drives.

I know one thing to be true. there is either a huge variation in milage on the newer cummins or there are alot of people who like to lie about it. I have seen from 13-14 all the way up to 23mph posted. so translation some trucks are either lemon's or poeple are full of it.

 

I had 80k on the 04 Dealer assures me they are 3;73s on the 06 and the mpg's are hand calculated. 22mpg most of the time on the hiway empty Thanks, I will try to be patient

 

arcojet-
I hear you. I just bought the '06 and traded an '03 that was good for 21mpg hwy and 16mpg with my trailer. So far, my best hand calculated is 16.6mph hwy and a whopping 12.4 with trailer over this past weekend.

With what I hear about fuel prices in the coming months.........O U C H ! ! !

 

Mines 18.1 according to the over head and thats witht he edge on level 4. I also idle alot during the day.


.

 

the 600 series motros just don't get the mileage. MY friend has an '05 dually with the NV-5600...I have an '04 305/555 with the 5600 also. Both have 3.73 gears. I get at least 2 MPG better than him on every tank.

Mine also must have just 'broke in' at about 25,000 miles. I have been doing some hauling and am very pleased with the mileage there...BUT my empy mileage has suddenly jumped by almost 2 MPG. I used to get 17 MPG with mostly city driving...my last tank put me at 18.8 MPG with the same city driving.

I agree...get some miles on it. It won;t get as good as the older motors...but you should end up at least a little better than where you're at now.

 

My truck is an early '05 325/610 2 wheel drive and I have had just the opposite experience. Given I'm running the 48 re on flat roads so I run 68 mph at 1900 rpm. I haven't towed my Autocross car since I purchased the truck in December, but commuting about 80% highway I'm getting over 20 mph average hand calculated over two tanks of fuel. My truck is stock, plastic intercooler ends and all.

I have taken all the precautions of filling up at the same station, same pump, etc. For these two tanks I ran Power Service Diesel Kleen, but after reading about the actual content of PSD (mostly diesel fuel) I decided I would skip it and see how it does. I'll be filling up in the next few days and it looks like my mpg is going to be the same or a little higher.

In the next couple months I'll hit a few autocrosses and do some low speed towing to help with the break in. Hoping to see my mpg steadily rise another 1 or 2 mpg.

I think the biggest single effect on mpg with the 325/610 is the gearing and resisting putting your foot in it!

Ryan

 

I have a 04 325/600 with 4.10 gears and a 48RE. I was getting only 15 mpg and I don't cut it any slack. 75mph on interstate. I did have one issue. My High pressure fuel pump was leaking. I just had it replaced and it seems to be doing about 2 mpg better. The truck has 27,000 miles on it. Pulling I am only getting 12 mpg.

 

mine started new with 13 miles on odometer getting around 14 mixed city/town driving and 18 highway....now at around 2500 and the ROKKtech sensor changed I am getting 15.3 city/town during week and on a trip from Charleston to Myrtle Beach with a 80% highway and 20% in town mix I averaged around 19.3. I topped off in Mt Pleasant.....drove up...drove back...topped off again and did it by hand.

This is with stock 265 tires, 3.73 rear end and Auto tranny....keeping speed at slightly below 1800rpms which is about 64mph in my truck.

Going up to 285 tires soon but hope to have enough miles to go full synthetic in motor by then.

my overhead is within =/- 0.3mpg of my hand calculations.

 

Im glad to here that somebody is gettin good mileage cause I am getting about 13-14 average mpg with the overhead but I cant keep my foot out of it. I can admire you guys with the patience to drive slow and get the good mileage but I just cant. I just love that feel of high torque layin ya back in tha seat. Kinda immature but lots of fun. Plus as a subcontractor I charge all my mileage back to the customers at .50 cents a mile unless pulling a trailer and then its a dollar a mile. I did one time try to see what kind of mileage I could get from Missouri to Tennesse and I coasted down all of the hills in nuetral and never broke 65 miles per hour (i wasnt too excited about getting to that job) and pulling into the plant I was at 19.3 on the overhead and I really tried tha whole way. I lost a bet too that I could'nt get 20 and they were right. Guess theres another case of beer I cant ever get back.