I recall it taking at least 15,000 miles before I was getting decent fuel economy on my 5.9 - same with the Navistar 7.3's.

Is the 6.7 really that bad? I have over 350 miles on mine and almost getting 13MPG. I'm expecting 17-20 (city) like my 5.9, but after 40 fill ups

Does anyone out there have a 60,000 mile 6.7? Can you comment on the fuel economy of a worked 6.7? Is it really that bad, or are people impatient?

 

Have 49400 miles and NOT EVEN close to what your looking for!
Hand calculated I'm getting about 18 highway and 12 city AT BEST.
The VAST majority of my driving is Highway as Idrive back and forth to my office bi-weekly and it is a 610 mile trip one way.

 

there are a couple of people here that have way over 50K and still getting crap milage. Just face it, you are goig to get about 13-14 city and about 18n hwy

chris

 

Mine gets 17-18. My driving is about 70% hwy and 30 city. Before the last recall/reflash it was 16-17mpg. Odo says just under 14,000 miles.

 

I'm getting 15mph city, but I drive it like an old man. 17 mph highway. I guess we Gota face the poor MPG. I have 4300 on the clock. I hope it improves with time.

 

122k miles on the clock. Over half of those miles are towing something, usually heavy - 10k to 14k. Most of those miles are highway - usual cruise @ 75 m.p.h. With minimal wind I get about 15.5 to 16 m.p.g. empty and towing anything 8 to 10 m.p.g. again @ 75 m.p.h. If I slow down to under 70 m.p.h. I might get an extra 1 m.p.g. I have burned about 1k gals. more fuel getting to 100k miles with this truck than I did with my 04.5. Sorry to burst your bubble, mine burst a few thousand miles ago.
On the bright side though, NO repairs getting to 122k miles - pretty much just the routine maintenance stuff. That really helps!!

 

Which is the same or slightly better than my 01 did.

 

The strange thing is that with the 6 speed auto the rpms are so much lower but the mileage still isn't great. Driving home from the dealership in NC I noticed that the overhead would start reading higher if I was driving 80mph versus my normal of about 72mph. Next time I'm on the hwy I'm going to try leaving it in 5th gear instead of 6th and see what happens. My 5.9s always liked 1800rpms for optimum mileage but the 6.7 seems to like 2000rpms better...
I hate to say it but the only way to get big mileage gains are by adding illegal items to these trucks....
I'm pulling all the junk out of my intake tube this weekend. That's gotta help some. That big center tube has all kinds of sound deadening stuff in it. So much that you can't hear the turbo at all. has anybody noticed any real gain with an aftermarket intake?

 

14 would be a lot better than I am getting on the highway. I get 11-13 highway 9-10- pulling. $4 diesel and I am going to find something else to drive

 

Man, thats a bummer! At 13.2 hand calc average around town my truck is getting parked for my bike as soon as my knee allows!!

Chris

 

Well that's a pooper... I'll keep an eye out for the smarty then. It was the best thing I did on my 5.9 for fuel economy. I really don't need any more power out of the 6.7, but I guess I'll need something that will allow me to shed some extra (fuel consuming) parts without tripping codes.

Thanks for your replies

 

I thought about abike but it's been so long since I rode one that I'm kind of scared to get back on one. Especially to sit in traffic here.....

 

I have 33000 miles on my truck and life time avg. is 14.00 mpg. All types of driving and towing.

 

I agree with Dodgezilla about the best mpg (16 empty) being at 2000 rpm, But that's only about 68 mph with my G56/3.73's. Towing our 5er I get about 10mpg.
I'm considering the gearvenders overdrive unit and would like to hear about any experience anybody has had (good or bad) with them. There expensive but it would get me back to 75mph or so at 2000 rpm and I think would pay for itself over time.

 

hey dodgezilla,
I have 10,000 on mine, and was gettting about the same as most of the folks. 13 cty., and 17hwy. although in the 2 weeks prior to the new 35's, it was consistently hitting 19-20mpg. on hwy. actually saw 22.5 on the way to get the tires! But now that it's outta calibration, the numbers have obviously dropped on the guage. trying to work out the math between stock and new tire sizes and what the computer is thinking, (which will give me my actual decrease from the bigger shoes) is my next move, but anyway, in an effort to regain mpg., the AFE 2nd stage intake went in wed.s.. Definitely hear that turbo! man, you'd never know how much that sucker is working when running the stock airbox. Jakebrake too. the new tire average mpg's went down to 12/15, and then with the new air intake, more like 13.5/16.5. but that's not reality, need to program the new tire size into the computer for that, any thoughts on programmers?
Still want to squeeze more mpg out of it though. thinking about a fuel booster..thoughts?