Currently getting 15-17 city, 18-21 highway running around 80mph and 12-14 towing.

 

last week was the best ive ever got with mine, i got 635 miles out of a tank which would put me in the low 20s, i had a 95 that i got 28 miles to the gallon all day long,the 12 valves seemed to always do better on the fuel,brother in law has a ho 6spd ive seen 700 miles out of a tank on his

 

My truck likes 19-20 MPG mixed driving. The 4.10's and auto are a hindrance, as is the added wind and road resistance of the dually. The killer for me is how I was getting 11-12 MPG doing the exact same driving, only possibly slower, with my 2001 V-10 2500 Sport 4x4, also 4.10's and auto. I love my CTD!!

 

Just got back yesterday, Knoxville, TN to Atlanta, GA round trip. I had plenty of time so I thought I would check my mileage at different speeds.

My truck is 3/4, 3.55, auto, unloaded.
With cruise @ 65mph I got 23.6mpg according to the computer.
On the way back I decided to check other speeds.
I set the cruise@ 60mph and got 25.2mpg. I ran the truck for 50 miles and then checked the comp. for the above mileage.
I then set the cruise@55mph and got 27.3mpg.
I normally drive at 75mph and get anywhere from 18.5- 19mpg on the same stretch of road.

So, I am going to drop my speed to 65mph from now on. It doesn't take THAT much longer at 65vs75, No way am I going to drive 55mph anymore, there were bugs flying by me!

 

i just turned a 2682 mile loop from southern az to id and back through wy pulling 10000+ and averaged 8.67mpg. all speed at posted plus a little show up the duramax pulling a tiny box up 6% racing on the way back, just couldn't resist. the truck just amazes me. i wish i got the 15 or 20 everybody else gets pulling this weight but i can feel the work the engine is doing,seat of the pants, and visually on the gauges. i think there's some duramax blood on my hood, oil streaks streaching from the snout to the windshield, didn't mean to hurt it, this truck rocks, and 8.67 is fine with me if thats all i get.

 

I get 19-21 mpg in the city, and 28-31 on the hwy. Now before you americans jump the gun and start thinking i am full of bull kaka this is in imperial gallons. So this works out to 14-15 in the city and 19-24 on the hwy for you guys.

 

Dash computer is showing an average of 16.8 city driving with an average of 30-35 miles a day. I'm taking a 1,500 mile round trip middle of next month, curious to see what I get on the highway.

 

OK, not sure how to ask this question, with our getting sent to the corner for asking a dumb question but, I just don't understand how there is that large of a difference in mpg? I have tried driving like an old woman for an entire tank, trying to obtain this better miliage. It really did not change much not even 1mpg better, heck I can't seem to top 16.3 however I can drive with 20' box trailer at 75 mph, and not drop below 13.5. I would think it has to do with the gearing. Since most of the time my truck only has my family in it, what is the gearing one should strive for? Take it easy on me, I have tried to read as many post on this that I could before asking, I know that I probably missed the one that I needed.

 

Well, I seem to do well with the diesel for fuel mileage. But I do enjoy the power that Cummins produces. No matter how hard I try I can't seem to keep the GO! pedal off the carpet!

But still I get 20 MPG with it!

 

Mileage differences come from 5 basic things
1-2500 CTD vs 3500CTD
2-4.10 rear ends vs 3.55's
3-Auto vs Manual trannys
4-Overhead consols (usually inaccurate) vs actual calculations.
5-Trucks over vs under 40,000 miles

The last item has to do with break in time for the Cummins. I gradually picked up 1.5 mpg from 35,000 to 45,000 miles. Those that tow heavy seem to get this gain earlier, which makes sense.

RJ

PS - Many here feel your right foot is biggest factor, and it's obviously important...BUT, I'm with you primetime; I tried a 300 mile interstate trip at 60 mph and it made no difference from my around town mileage??

 

Rjohnson hit it on the head with the exception of one small item. I have noticed that if my tires tend to drop in pressure to 35-40# my mileage drops from 20-21 to 17-18.5. Whwn I repressurize tires back up to 52-55# my mileage goes right back up. My driving style stays pretty constant in that I speed shift most of the time w/out using clutch except to take off. Driving consists of 40% city and 60% highway and the truck now has 120K miles under its belt. Since I work construction my tires tend to pick up pointy pokey objects on a regular basis, so I am constantly checking tire pressure...

Gary

 

Gary's absolutely right - one other (not so small) item.

6-Low (soft ride) tire pressure vs higher mileage, max pressure.
and maybe..
7-Big differences in empty weights...towing equipt., bumpers, toolboxes, bigger gas tanks, bed lenghts, 4x4 vs 2x4, etc.

I'm now up to 18+ mpg; with a 4x4 and automatic on a 7450 lb truck...I'm happy! Wish I knew why I have never gotten a 2-3 mpg jump on hwy trips??
RJ

 

I'm with you, FastSS! I'm so jeleous reading everyone elses' great mileage. Today I zero'd the mileage counter and then drove up hill and down the other side to where I keep my horse, and it dropped down to 12, never saw above 14 even though I can coast four miles at one point without ever touching the gas pedal!

I filled up afterwards and calculated 14 mpg average, combined city/hwy. Ick!

I'm hoping to bomb our truck so it can do so well! What else could be wrong? We've only had it since the end of May and have put about 1K on it.

betsycam
'99 2500 CTD, QC 4X4 LB, all stock except 4" exhaust

 

OK, so, the gears, and auto vs manual 2500 vs 3500 2wdr vs 4wd, under stand now on to the more interesting question, do the mods they speak of acutally actually improve mpg? I know there is an increase in HP, and tork. It just seems odd that they would not install better injectors up front? Or this black box that that snaps in I think that they call it edge or something similiar. Thanks for your responces things are starting to come together. And oh by the way someone slap that moron that increased my fuel by .15 over night was shocked at 1.74 here in St. Louis

 

Well it not the mods that make the fuel mileage. I'm completely stock yet on the engine. All highway mileage. Approx. 7,900#... So that not the answer...

There is something else that is dragging you down... Tire size, tire pressure, dragging brakes, Etc...