I've been tracking my mpg for a few months, as I've been taking trips to NY for a move. About 420 miles each way hauling my 20 ft. landscape-mowing trailer with furniture & stuff (nothing major). I avg about 14mpg at 70-72mph on the interstate. I ease up hills & set cruise for flat stretches. 70--72 puts me at about 1900 rpm. This is hand calculated off each qtr. tank on the gauge, from full to 3/4, then 3/4 to half tank.
I read in my diesel power magazine about their mileage experiment a few months ago, so I made some plastic pcs. to block off the grill, aired up my tires (uncomfortable ride for 7 hrs), pulled my mirrors in, & kept the windows almost all the way up. One way with the trailer empty, I calculated close to 17mpg! Return trip was about 14mpg with the furniture on the trailer.
The next trip I did the same, but had the AC on trickle, & it knocked me down to 12!!!!!!!! Holy crap that angered me, but I had to to stay awake (all trips were in the middle of the night).
I get about 13 or so with just stop & go city driving, which is almost twice what I get driving my gas dodge on the freeway!
I almost wonder if someone put 4.10's in my truck; maybe I just need it tuned. The badges/stickers say I have 3.54's, but I also drive about 72 on the highway, & I am pulling my 20 ft (24 ft total) lawn trailer. I have 235/85/16's on the rear to keep my rpm's down. At "70" on the speedo (actually is about 72), I'm running about 1900 rpm. Does this sound right?
Thanks guys

 

I get an average of 15 city and 18 hwy. My best hwy is 19.8 worst is 17. This is hand calc. My overhead is usually off by +2. My best city is 16.4 and worst is 13. My city driving is all stop and go traffic with almost no hwy. A lot depend on how I drive in town, I think I could get 15.5 to 16 every time if I could stay out of it.

 

I drive two 05's regularly.
The yellow one that's my pic is my personal truck. Reg. Cab, Long Bed, Auto. I've seen just under 19 mpg driving it at 60 mph. I've also seen considerably less driving interstate at 75-80. I tend to drive like a grandpa.
The truck I drive at work is a 3500 quad cab auto dually. I have seen up to 16.5 mpg highway. It typically spends a lot of time idling though, so avg. mpg are around 14.5.
All my #'s are hand calculated.

 

highest 20 lovest 13 so about 16 average

 

Just got my truck about 3 months ago, have been getting between 20 and 24 mpg, 60% hwy, 40% city, always empty, running on biodiesel, driving and accelerating slowly. I seem to get about 24 when I add isopropyl alcohol, and in the 20-21 range when I don't add it.

I'm thinking of adding propane, or maybe even hydrogen to see if I can get even better mileage...

-Matt

'95 2500, ext cab, long bed, auto, 356k miles.