Gentlemen, thanks for the responses. I have the Cummins 600 with 325 HP, at least that is what was on the sticker when I bought it. Next time I get to the dealership, I'll see if they can run diags to see if something is wrong. As far as drivability, it seems fine.

 

Ran ~500 highway miles this weekend.
We averaged 18.5mpg at ~71mph. (kept the motor at ~2000rpms)

If I go above 2000rpms, milage drastically drops. (2200rpms = 75mph= ~16mpg)

~Nate

 

hmm. 2000 rpms is about 67-68mph for me. Looks like we have the same setup except for you have an auto. I'll have to get some bigger tires

 

2000 rpms for me is around 72 MPH. i still can't break 18 MPG no matter what speed i run?

you guys that are saying that you can get over 20MPG with a 610 i call BS!!!!

britt

 

t-7, I haven't gotten over 20 yet either but I don't drive much in the flatlands. I bet I could get 20+ if I drove 60 on I-70 across Kansas. I've only been to Arkansas once but I remember it being pretty hilly. Also you've got 2 strikes against you compared to a lot of these guys. You have an auto and a dually. Both aren't conducive to better gas mileage.

 

Oh I agree with you.... but my 03 (which was exactly the same as the one I have now except it was a 555 6 SP) would regularly get over 20 mpg at around 60-65 MPH. The freeways around town are mostly flat and I mean flat! I didn't buy my truck for mileage but these guys that are giving these outrageous clams such as over 20MPG with a 610 I still call BULLS*&^ on. They are lying. No other way around it!

Britt

 

SRW 1 Ton Auto Short Box and i cant get over 16.5 best so far that was babying it. Also The 72 MPH=2000RPM also

 

I have the 600 with 10K miles on her and my best milage has been 24.5MPG hand calculated. I have done this twice. Both times were running 60MPH through the mtns of VA and WVA unloaded. However my average is lower at 18MPG because I usually end up on the interstate. On occasions that the diesel goes to work it gets 17+MPG in a 6 mile each way stop and go traffic. That is why I usually drive the gasser to work. Hauling a load on the interstate she gets 11-12MPG. I usually start off in second gear and shift between 1600 and 2000 RPM. Light throttle and staying at 60MPH is the key. I also found that the truck gets better milage in VA than SC by a few MPG. I usually run fuel from BP with no additives. Oil and fuel filter changed at 3000 miles and 7500 from there on. I have not done the milage flash. I know there is alot of info but maybe I stumbled onto something. Good luck with your milage.

 

I HAVE A 2004 QUAD CAB DIESEL 4x4 with an automatic and 3.76 gears. 325 horses at 2900 rpms is what the side of the engine says. I drive it around town and baby it. I never really get on the throttle and I have only 1070 miles on it so far. The truck only gets 13 and a half miles to the gallon. I was told that the truck would get almost 20. When will this happen?

 

it won't happen.

sorry to give you bad news.

britt

 

i almost forgot.... if your truck falls within the sn#'s then you might be able to get the mileage reflash. this will help a little but i doubt it will get you above or anywhere close to 20MPG.

britt

 

You naysayers are making feel lucky I got a good truck. I just filled up today and hand calculated 15.43 for my last tank and that was about 50/50 hwy/city. That included plenty of idle and warmup time too. I am positive that if I went on a road trip I'd be over 18-19 even on the winter blend. Over twenty sounds very possible to me next summer when I get a few more miles on her. I'm only at 8200 now and have had the reflash.

 

My fuel mileage has improved steadily on my 04 six speed since new--now 10k. I had the reflash done and noticed improvement also. I recently drove 220 miles--all highway and 60-65mph. I hand calculated my mileage at 20.4. My overhead read 19.8. Two recent fillups following my 220 mile road trip--a mostly to and from town were about 18.5, and my overhead was right on target both times. Currently I have 120 miles on my odometer--two 50 mile round trips and the rest in town--all driving conservatively. My overhead reads 20.1. All the above is on winter fuel supplemented with Stanadyne PF.

 

I got the flash and have 10k on it. The stupid computer says 21.3 MPG and yes i reset it everytime but hand calcs. Come out differently to around 16.5 at most. Are you people getting 20 filling up to the same spot everytime?

 

I fill up to roughly the same spot every time and usually run the tank down to empty. It usually takes me 32 gallons to fill up. I try to get it almost to the point of overflowing the nozzle once the foam goes down.