a week ago i ran through about 1/2 tank of fuel @ 17.2 mpg. The next day, over the same roads I avg under 14mpg on the rest of the tank. The next tank went back to 17/18 mpg. This week I ran through the first 1/2 tank @ 18.3mpg and the next day, over the same roads I am down to 16mpg on the remaining fuel.
Is something going on that should concern me?

How big is ur right foot on ur bad mpg days? :grd:

BTW - A little info about ur truck would help, signature...

Later . . . . . .
6 Shooter

A little info about ur truck would help, signature...

What he said!

Fuel filter might be getting plugged up. They are only good for about 10-12,000 miles. GM says 15, but I can't get to 15 without it plugging up and causing the truck to slow down and get bad fuel economy.

And yes, some info on the truck always helps. Set up a signature, with at least a brief description of your truck. :)

even wind can change it that much. A decenty head wind has knocked almost 4-6 MPG off of me in the past, and that is empty

How are you determining the fuel consumption on each of the 2 legs?

Where I buy fuel from has alot to do with my fuel mileage. Some places give me really great fuel mileage and others make me think I have a problem with my truck. Just something else to consider.

Hop

How did you figure? Can't really judge it by the needle in the gauge. Truly- fill, drive, refill and calculate is the only way to tell.
By the needle, my first half is always slower to go , about 300miles, then the second half is a joke,125 miles.

Why is that?

My mpg varries depending where I fill up. I always try to get fuel at big truck stops. Fuel is fresher and I tend to get better mpg.

That's a good idea getting the fuel there. The one in Va. Beach charges to much!!

check these numbers out, I had about a 75 mile trip I was on last week had the cruise set most of the time around 74mph until the very last where the road dropped down to two lanes then it was 55. The truck clicked off 23.0 mpg just as I pulled into town. The truck was empty and only had 1/4 tank of fuel so I know this helped. Do you think these numbers are accurate? On the way back I had 250lbs in the bed and I filled up while I was in town, only dropped a little to 22.3 mpg. I was impressed to say the least. This is my 3rd first gen duramax and niether of the other ones got better than 14 mpg. The truck is an early 04 crewcab dually with the lb7, allison, edge box on stage 3 and the tires are 235/85 instead of the stock 215/85 other than that it is stock with 64k on the odometer, not even a knn filter yet. By the way it is an LT with steering wheels controls that will give you average mpg and this is where I got the numbers from.

My truck get around 12 mph here in the mountians and around 14 to 16 on the highway running empty. That is what the computer in the truck said. I going on a trip this weekend and i going to hand check it.
Will let you all know when i get back.....
I have A 4X4 4 door dually duramax and allison........ It has only 13000 miles on it. I have 265/75/16 nitto at..

By the way it is an LT with steering wheels controls that will give you average mpg and this is where I got the numbers from.

not at all. The edge will make your mpg look better and so will the tires. Have you calibrated your speedo for the tire size? I don't think Edge can do that.

Have a friend clock you with their vehicle.

Do a hand calculation to check accuracy. I would bet you are somewhere in the 15-18 mpg range.

One thing I like about the scanguage for checking mileage. There is a way to correct it with fillups. You enter the amount of your fillup, it figures the % that it is off. My truck is always within .2 of hand calc:)

My Dulley is stock and has 31000 miles on it. I took my daughter back to college today in Pittsburgh, Pa. I filled up right to the top of the fill neck and drove at 70 mph going to Pittsburg and had to take some back roads coming home due to traffic on the Pa Turnpike. I filled up on the way home at the same station I filled up at in the AM. I drove 340.8 miles and filled up with 18.9 gallons. MPG was 18. :) I think thats pretty good .
Cosgr:D ve

i just drove to dubuque from ne il[northbrook] and back 420 miles just truck and averaged 18.2 hand calculated ,speeds averaged 50-75

Cincinnati,OH. to Cleveland,OH. 20.3 MPG at 60 MPH hand calculated.
USA-1

Cincinnati,OH. to Cleveland,OH. 20.3 MPG at 60 MPH hand calculated.
USA-1

With all the construction delays, 60 is about all you can do on I-71....:rolleyes:

Certainly can't complain about 20 mpg out of a big dually. I only unhook the trailer from my dually for service, so I have no idea what it does yet.
I have to deliver a trailer to MO this week, running home empty. I'm looking forward to checking it out. The truck won't know what to do, this will be the first trip (return trip) without a trailer, currently has 55,000 miles. Running with an 18,000# trailer, it gets about a solid 10 mpg.

Just ran 300+ miles from central OH to the Allegheny National Forest in PA. Averaged right around 18 mpg. 55-79mph

I am a big believer in the difference in fuels. I fill up at our coop usually more expensive by 4 to 5 cents a gallon but the difference in MPG makes up for the difference in costs they call it premium diesel fuels. There are different grades of diesel fuel and a rating like octane (nictane?) just cannot think of the word just yet. Mine gets the best mileage at just over 2200 rpms. at 27000 miles the mileage just keeps getting better.
My friends told me a long time ago about the premium diesel fuel and I never listened, now I am a believer. Of course gelled fuel will change your mind fast.
BTW to colder the temp the better the mileage that is if you do not let it warm up for 30 minutes.

at 70 i get about 500 miles to the tank. unloaded. making a 500 mile trip with a open trailer and a car next week.

Take a Silverado add dually and fenders throw in crew cab add transfer case front axle = instant decrease in MPG

Over Thanksgiving week I made round three trips to Denver from Colorado Springs, which means 6 trips over Monument pass (steep incline). Along with about 100 miles of running in Colorado Springs itself. All on one tank of diesel. I got 16.97 MPG, hand calculated. I was amazed!

I am a big believer in the difference in fuels. I fill up at our coop usually more expensive by 4 to 5 cents a gallon but the difference in MPG makes up for the difference in costs they call it premium diesel fuels. There are different grades of diesel fuel and a rating like octane (nictane?) just cannot think of the word just yet. Mine gets the best mileage at just over 2200 rpms. at 27000 miles the mileage just keeps getting better.
My friends told me a long time ago about the premium diesel fuel and I never listened, now I am a believer. Of course gelled fuel will change your mind fast.
BTW to colder the temp the better the mileage that is if you do not let it warm up for 30 minutes.

I believe it is Cetain that is the level they use to rate Diesel fuels.

Mine is a 3500 4x4 DRW crew cab. I get 15.5 to 16 mpg at 78 mph on the interstate. Not bad for a 7500 pound truck at that speed. At 70 mph it goes up to 16.5mpg. This is hand calculated. If I could drive 60 to 65 mph I could break 17.5 mpg.

mine gets about 16mpg highway or woods

I drove from Missouri to Colorado springs going 75 and got 7-9mpg pulling my 5er, then when I was in Colo. Springs I averaged 17+ with no tuner, stock. unhooked....must be the air/fuel mixture in Colo. Springs.
But now I am not stock.

So I have a few more questions to add to this thread! How many miles do you need to put on these trucks before the MPG gets as good as it is ever going to get?

Also, I have the more agressive factory tires and although they sure aren't super swampers, with six of them on the road, they can't help the MPG I'm sure!

Almost the last thing I did in 2006 was pull into a Get Go station and got 30 gallons of fuel for free!! Was an awesome feeling! Was funny having the girl working there ask if I wanted to use my fuel perks and then watching her face when she real noticed I had $2.79 a gallon off!

Ken

I have two dually's and many friends with them also. I gues some of you guys got all the "good" ones! My mpg is always around 16 empty. I bought the truck to tow so it's fine with me. Where does all this 20mpg come from:eek: ? Also if you bought a 40k+ vehicle why do people complain about fuel prices? (not directed at anyone personally) It just seems that local camping people are always crying about mileage and power. My truck stock will tow a city block and get 14mpg. I guess my rant is how can you spend almost 6 figures to go camping then complain fuel went up 20 cents and you are now going to spend 4k in mods to get another mile per gallon.:)

I drove from Missouri to Colorado springs going 75 and got 7-9mpg pulling my 5er, then when I was in Colo. Springs I averaged 17+ with no tuner, stock. unhooked....must be the air/fuel mixture in Colo. Springs.
But now I am not stock.

One advantage of a turbo diesel is that they do not know when they are in the mountains...that's what the turbo does for you. Gassers lose about 3% of their power for each 1000' of altitude...so in CO, at 10 to 13,000 ', 1/3 of the gassers power is gone.

Hand calculate it dont guestimate or trust the dic

One advantage of a turbo diesel is that they do not know when they are in the mountains...that's what the turbo does for you. Gassers lose about 3% of their power for each 1000' of altitude...so in CO, at 10 to 13,000 ', 1/3 of the gassers power is gone.


Good point - When i went from my house in Salinas, Ca (Monterey) to Reno, Nv i swear my old sierra felt lathargic all of a sudden. I remember pulling off the highway and onto the roads trying to merge. I kept wondering what was wrong with this thing.

I am telling you all use Enviromax Plus in fuel, works great to boost power back up in diesels, in mean awhile boost MPG too. If want to know more just message me.

The best that I can get empty on my 6.5 dually is 13.5 to 14.5 MPG, that is running under the following conditions:

1.- The measures are using the stock odometer and trip.
2.- Empty
3.- Using 4.10 gears.
4.- 2" lowered wheelbase
5.- 225/75-R16 tires
6.- Uneven roads with plenty of hills
7.- Driving around 60-65 MPH (2,100-2,250 RPM's)
8.- Using Mexico's only #2 Diesel available, which is good stuff and goes for somewhere around $1.90 a gallon. but I am not so sure about how high or low is on sulfur.
9.- Running a qt of 2 cycle racing oil on the fuel tank for every 32 gallons.

I see that I am located somehow on the lower end, and that might be because of my particular conditions...:mad:

Drafting a semi at 70 MPH is the ticket! It reduces drag...but, on the other hand, it's not safe.

Drafting a semi at 70 MPH is the ticket! It reduces drag...but, on the other hand, it's not safe.

Sounds fun, just like what we do on any type of road racing, get close behind the car in front of you to get some "Suction Effect":)

But like you said it's not safe, especially if you see the dangerous cargo marks on the semi...

One advantage of a turbo diesel is that they do not know when they are in the mountains...that's what the turbo does for you. Gassers lose about 3% of their power for each 1000' of altitude...so in CO, at 10 to 13,000 ', 1/3 of the gassers power is gone.


Aint air air? Less for the turbo to work with, the fuel still mixes with the same air the gassers mix with. The turbo doesn't make the air richer... it doesn't add to the make-up of the air...just compresses more of the same, hmmm.
Not arguing with you Soldier- just trying to bet my pea brain around this.:p: Inlightin me sommore. Why did I get better mpg up there?

have you ever gone from sea level to up in the mountains and felt kind of light headed and short of breath?
It's the density of the air that changes, it's thinner up there :)
When we goto reno, or when i went to visit my grandma in Colorado the first few days all i did was sleep because of it. LOL

I find that the botom half of most GM's are less then half so this may cause the lower mileage. I go 400 KM on half a tank and fill up and it takes 75 - 80 liters run it empty it takes 130 so have should be 65.

I find that the botom half of most GM's are less then half so this may cause the lower mileage. I go 400 KM on half a tank and fill up and it takes 75 - 80 liters run it empty it takes 130 so have should be 65.

??

I find that the botom half of most GM's are less then half so this may cause the lower mileage. I go 400 KM on half a tank and fill up and it takes 75 - 80 liters run it empty it takes 130 so have should be 65.

:drop_mout I need this translated please...

I do believe the point that he was trying to make is that the first half of the fuel guage reading you can travel x number of kilometers on a litre of fuel. The 1/2 tank reading on the guage is more like 35-40% of fuel capacity remaining.

Clear as mud Eh ?

I guess I understand the same as yo-yo:

That somehow it takes more miles to get the fuel meter's reading from completly full to 1/2, than the miles it takes to get the meter from 1/2 to empty.

I feel that same happends with all Chevy fuel meters, gassers and diesels since a long time ago...