I have a 2006 6.0 crew cab short bed 4wd. The truck has a 2.5 inch leveling kit, 4" silverline turbo back exhaust, and a S&B intake. I do not think it is possible to drive the truck any easier than I do. I rarely get over 60. If I do we are talking 65. I coast to all stop lights and take off easy. I feel I should be getting 18. Is that unreasonable?

 

What tires/gears do you have? Has your speedo been re-calibrated for this? If not, are you hand calculating these answers? If you are hand calculating AND you have larger than OEM diameter tires, what correction factor are you using?

Until those questions are answered, you're information is incomplete.

That being said, when I hand calculate (35" BFGs and 3.73s), that's about what I get when cruising in Phx, Az (1300ft asl). At home in Fallon, NV (4000ft asl) I'm lucky to see 14mpg cruising around town. I included ASL because it makes a MAJOR difference in my mpg.

 

18 City is going to be a stretch. I get 15+ on my daily commute driving. HWY is better than 17+. FWIW I just ran 470+ miles with 1/4 tank left on a 38 gallon tank for my everyday driving.

 

I have 4.10 gears and I hand calculate my mileage. I have stock 17" wheels with oem tires. I was hoping for about a 16 city/highway average and 18 on the highway. Thanks for the post so far. Again, I am just trying to see where my mileage falls with everyone else.

 

Mines a 6 speed manual 4wd with 305 70 at and I got 17.3 pulling a 20 ft gooseneck with my mud truck and I get 18 plus as a daily driver. I have seen a 23 mpg tank before. I'm not bs ing here I drive like I'm an old man 90 percent of the time except on occasion I like to hear it get loud. I'm really sure this is not to be expected but has been nice considering I drove rangers up until this truck and they didn't get as good mpg as this truck. My buddy has a stock 05 dully and he get 14 mpg unloaded. I'm thinking the manual helps out a bunch.

 

I will never believe a 6.0 to get 23mpg, just my opinion. Most people don't even know how to properly calculate the mileage in a super duty because they put in a different amount of fuel every time that isn't a "full tank." Just cause the pump clicked off does not mean your tank is full and does not mean it's filled to the same spot as last time. Must fill til fuel is sitting in the neck.

4.10's and stock tires are never going to net 18mpg. The RPM's have to be very high. That said, that's still close to what I was avg'ing with mixed driving highway and city, 15.3 or so last I checked. Probably could do 17ish if I drive easy. But I don't.

When the veggie system is up and operating I have avg'd over 100mpg before though :o)

 

I made a mistake in my post, I have the 3.73 gear. You mentioned if you drive easy you could get 17. I drive very easy and I can not get close to that. I did a 200 mile drive at 65 mph which was mostly flat and I got 15.3 by hand calculating the mpg's. Looks like the SCT tuner may be the big difference between you and I. I am currently saving for an X3. I almost forgot, what size wheels and tires are you running?

 

I averaged 14 with a 05 f350 single rear wheel 4x4 auto with a edge juice best I ever got was about 19 driving from nd to Texas and back

 

Iv'e seen a 24mpg but that was a one tank run, left Maryland and drove straight through to Georgia without stopping, I run stock size tires set at 80psi rear,70psi front/ recommended for front os 55psi but I found that realy hurts the milage. I see 15-16 when towing a 34ft enclosed gooseneck trailer with 7'6" interior height with aout a 5000lb load inside it. When just using it for work I average 18-19mpg, normally 60 miles one way, if I have a week where I sleep a little later, I will drop down to 16-17mpg as I will be doing 85mph to get there on time.

 

I get the same mileage as you. Honestly I haven't checked it in so long. The last time I checked it was probably 4 years ago. I loaded up my economy tune and drove like a fuggin putz. I didn't go over 2k rpms and TRIED to not go over 10psi of boost (try this sometime and you'll see how hard this really is). I avg'd 15.1mpg over a full tank. After that I said lets see how bad it is, loaded up extreme street, drove like a complete arsehole. I'm talking rolling burnouts, 100mph runs daily, etc etc.... avg'd 15.3mpg. Seriously. I never loaded the economy tune up again. I'd IMAGINE I could get close to 17 if I babied it with a race tune on. If you can drive like a sane person, a race tune with a converter lock up in all gears will yield excellent mileage. I don't have the self control for that though. I'm also picking up a TDI this weekend, so any chance of me calculating mileage is pretty much non existent. I did a rough mileage calculation before when I was running veggie and it was over 135mpg. I have a couple buddies who consistently have avg'd over 200mpg of diesel before.