18.5 sounds about right to me.That seems to be where I have leveled out at.I broke 20 mpg once.Can't seem to duplicte it tho.-Andy.

 

I average 18.5 on winter fuel doing 70-75 MPH. It goes closer to 19.1 if I'm driving up the center of Indiana on state highways doing 50-55. On summer fuel, it jumps up 1-2 MPG. I've seen 23 driving 45 on backroads to work. Can't remember if that was hand calcd or overhead lie-o-meter, but it's consistently +2 over hand calcs. My drive up the CA-1 from SLO to San Fran was 20MPGs on winter fuel. Of course, I was averaging 40 MPH. That was two years ago. I also saw 13 MPG on I-10 in west TX.

I'm running a Smarty 4.11 (IIRC) and not sure what settings it's on, as I just got back from Iraq.

 

I have a 2006 3500 4X4 mega cab with a automatic and the best I have ever gotten is 14.2 .monitor always shows about 4 better than what it is.I usually get between 11-12 however the last 3 fills have been between 9.2 and 10.3.The dealer claims there is nothing wrong with the mileage it is what everybody gets!I am running it empty and getting this and if I pull it the worst has been 7 the best 9.Not happy with this truck at all.I have tried smarty and all that did was make it smoke and get worse mileage.Tried edge got a little more power but lost mileage.Any other suggestions??Had 03 prior to this got between 14-17.5 loaded or empty.01 before that got between 16-22 doing the same work only difference is the 03 had 6 speed and 01 had 5 speed.

 

Sounds to me like you need to find another dealer. IMO that's BAD fuel mileage and something isn't right.

 

Did you loose mileage when you changed to 35' from stock?

 

If your overhead is accurate it'll be the first I've heard of. Usually they are optimistic 5-10%. Assuming 10% on yours, you were actually getting 17.55, that sounds about right.

 

Hey valv.. Have you adjusted your valves lately? I have basically the same setup as you and after re installing my engine I adjusted my valves. My mileage went up alot. haven't hand calc. yet. BUT before adjust the overhead read 16 and was usually hand calc.d within 2 mpg. Now my overhead reads average of 22 and although I haven't hand calc.d yet, I KNOW it's well over 14. And the funny thing is that my valves were still in spec, just at the limit. The manual says to not adjust, but I did anyway and took them down just below where they tell ya to.
For ex.(actual numbers not exact) within limits .06 to .14 do not adjust. Mine averaged .13
It says to adjust to .10. I adjusted them to .08
I've got alot more power too, but that may be due to the new rings I had previously installed. Never got "on it" til after break in.

3rd gear clutch drop used to chirp the duallies.
Now I leave 4 40 foot black marks without sweat. ooops

 

I went down to San Diego on the 22nd, and did 655 miles on one tank of fuel, and when I filled up it took almost 32 gallons of fuel. Anyways my overhead showed 22.4 mpg, and hand calculated was 20.47. I drove some flat land, some mountains, had stop and go traffic, and had the cruise set at 70 most of the way. the low fuel light came on about 30 miles from home, and I filled up back home. Anyhow, my truck has the bully dog tripple pup set on towing/econ, and is a 5.9 auto 4x4 that is stock and has a soft bed cover on it and just turned 15k miles....
When should one expect to have their engine broke in to see the fuel mileage, or am I already there? My old truck(I WISH I STILL HAD) was a 06 mega cab dually, and it would get 23 all day long on the fwy unloaded, but was a 2wd with the G56 manual.

 

I got mine (2004 3500 QCSRW 4X4 Auto) with 70000 on it in in Phoenix from a private seller and drove it back home and averaged between 18 & 19 doing 75 most of the way. I can get that well over 20 when I keep it between 50 and 60. At 65 I get anywhere from 18.4-19.7. All of the terrain around here is mixed with long flat runs, hills, some mountains, etc..
My future plans are to just help my truck breathe easier by opening up air intake and exhaust. All research indicates that these are simple ways for the average person to improve the mpgs.
My own personal advice for improving MPGs is to leave earlier and drive slower.

 

Mine broke in at about 40K miles, big rigs usually at about 100k!

 

I'm averaging 13-14 mpg. with my '07 w/10,000 miles on it and my 2,000# popup on 24/7. That's really babying it w/285-75-17 Toyo AT's. It's really the same as my '99 w/same popup on it. I do wish we could get the manufacturers to release a 275-80-17 tire. 34" tall and skinny. The Toyos really dropped the rpm's down to a realistic no. I've got Smarty Sr. Revo on sw#1 due to stock clutch.

 

I bet you're right. I havn't had the truck long enough to evaluate that. Still, the truck will get what it gets, because I drive like I drive everything else. I don't hot rod it, but I don't baby it, either.

I'm not going to spend a bunch of money to get an additional 1 mpg out of it. Not worth the trouble to me. Now, if I drove 40K miles every year, then it would be worth it. But I don't.

 

Kind of off topic, but if you gave up that arm, it might be a little hard to shift...

With 4.10 gears, I think 18.5mpg is pretty good. I wish I could have a 6spd in my truck...

 

My 2008 with 4.10 gears and auto trans goes 73 mph @ 2000 rpm with stock tires. TOM

 

I use to get 17, that was before I put my lift and tires on. Overall MPG is about the same, city droped a bit, highway a bit up. But even stock never over 17 MPG around 75-80 MPH, I guess I drive to fast

The std does help a bit though.