looking at getting a new 6.7. Had an 05 with 6spd and loved it. But i ve heard nothing but good things about these new 6spd autos. I live in the mountains...always swapping gears....and was wondering what the terrain would do to fuel mileage. my boss has an 06 with an auto and got 4mpg less than i got with my manual. and when i say the mountains i mean rarely getting above 55 mph, sharp turn after sharp turn.

so my question is if i get this new auto is the milege going to suffer because of it contantly searching for the right gear

im looking at a 3500 dually w/3.73

what kind of mpg are you guys getting?

 

I'm getting 17-17.5 unloaded in the hills of WV.

 

I live in western Pa. We think that we're in the mountains, but they're nothing like your Smokies. My auto doesn't seem to do a lot of shifting up and down. In fact it doesn't always downshift when I'd think that it should, and lugs a bit...nothing like the way that my V10, and the old 48's, behaved. With the auto, you can control shifts with the "paddle" on the gear selector if you chose to. And when in Tow/Haul mode, the trans downshifts when you want/need it to...works super slick with the exhaust brake. Regardless of the effect on mileage, I'd stick with the auto. Right now, I'm averaging 13...via calculator, not overhead...only 2700 miles on the truck...and that's in colder temps, with a bit of time spent carrying/pushing a 900 lb. plow.

 

Well in the mountains the ticket is to find your sweet spot.. both man and auto have 6 speeds, but the auto has 2 overdrives, so minus 1st on both you have 4 mountain gears with the manual and 3 on the auto.

 

I have the manual. I don't know how slow the curves are, but this 6.7 will pick up boost down at about 1200 so powering out of a curve is no problem, leave it in 5th and it'll do great. I get about 17 or better with mixed driving in the city and the highway. On the freeway this thing does better than my '00 did. On a trip back from CO to OR I averaged 21.9mpg. I would suggest test driving both in the terrain you'll be running and see which is better.

 

test drove an auto today....first impression is that it wastes a lot of rpms before the torq conv locks (after coasting and then getting back under load). i like the new auto, but i'm still not sure it is as fuel efficient as the manual.....

 

I wouldn,t say that the mans are the best as mine gets 9-10 pulling any little thing and the best I have gotten empty is 14 and I had to stay under 60 to do it, That was also the overhead and that usually says 1mpg better than it is. I have the 6.7 w/ 3.73's

 

14 at best...ouch...sounds like you have a problem...should be able to reach atleast 18 or so..... i know i had an 05 5.9 3:73 3500 dually and peaked at 20-22

 

I dont think that I am the only one that dosen't get very goog milage but I wish that I could get better. With just turning over 20,000 miles it should get decent but that just happens I guess.

 

I'm with you there..The best I've seen yet is 14.5 and that was hand cal!!!
I routinely get 13-13.5. I've only got 7200 miles, hoping for it to be better soon. I just got the newest flash(AV I think) and the truck seems to have throttle delay now, but mileage hasn't changed.
I guess I'm one of those guys that regrets trading a PERFECT 5.9 for this one. Oh well, live and learn! Good luck....Wish I was getting "coop's" mileage.

 

I have a 07.5 mega cab with the 6.7 and 6spd manual 3:73s and all stock have 4k on truck 50/50 driving and I get 16-17 but I only drive 62mph seems to be the best for me about 2000 rpm I love my truck had a 96 5.9, auto and all I miss about that is the loud 12valve noise

 

That's weird all, I get 18 with mine driving around town, and when we go over the pass to Nevada we get 20. Towing it's down to 14-15 but that is still good, can't complain, love my "07 2500 quad cab! It's a manual also.....