View Full Version : 8600 on the odo, still can't get 400 miles out of a full tank
I have a little over 8,600 miles on my truck. I run completely empty most of the time, yet I never get 400 miles out of my 34 gallon tank.
I typically fill up after 380 miles, and she takes about 32 gallons, for an average mpg of 11.9 MPG.
This is the milage I've been getting since I drove the truck off the lot.
I have done everything I could think off to 'break-in' the engine. Pulling 8000# for several hundred miles at WOT up grades and what not. No change in milage.
Is it just me, or is this 'average' for a 3500 CC LB with 8600 miles on the odo?
I got plenty of power as my 0-60 G-tech time of 8.4x @ 1100 miles show.
FirstDiesel
03-05-2003, 09:53
My stock 3500 with a cap averages 14.5 to 15.8 MPG on a tankful. That is city driving with short highway runs thrown in. If I take a long highway drive and don't pay attention to the speed limits I get about 16 mpg. If I stick to the speed limits I can get almost 18, very rarely though. smile.gif
I have about 14000 miles on mine now.
IndigoDually
03-05-2003, 09:58
Don't feel bad, I regularly only get 12-13.5. I have seen 420 once or twice but at 400 my low fuel light comes on. I saw 15 once but that was on a trip. Most of my travelling is on back roads and mixed with some highway with a good deal of idling. But when I try not to idle it does not really make much of a difference.
You are not the only one seeing low mileage. It is still better than gas though!
BTW i have over 20,000 on the clock with synthetic in everything except the trans.
John
[ 03-05-2003: Message edited by: IndigoDually ]</p>
Forgot to mention that my milage is almost all highway. I generally always drive 9 miles over the posted limit (so 64 on regular roads and 74 on Interstates).
Perhaps I'll torture myself and not exceed the speed limit on my next tank to see if that makes a difference. It will be painfull, but at least I'll know if my driving habit is to blame for my lower than average milage.
C5dura
a64pilot
03-05-2003, 10:26
I'm driving 1000 miles a week now. I too drive 10mph over whatever limit. I am averaging 16.7 mpg and get about about 525 between fillups. I am running essentially empty and about 95% highway now.
I have read that the 2003 has less power but it must get better mileage. Before the Juice 90hp, my GTeach said 8.7 for 0-60. I am averaging 18 mixed driving and I get over 19 on the highway at 75 mph.
I would be screaming if I was getting 11 or 12.
FirstDiesel
03-05-2003, 11:07
You have a 2500, we have 3500's. It seems the 2500's can easily get 18-20 MPG. The 3500'sa seem to mostly top out at 16-17.
I get 13-14MPG highway at 55! If I go 60 it drops back to 11-12... City is so bad I just don't check it. It would break my heart.
Still has plenty of power,, only 9K on the odo
Yikes - that sounds like terrible mileage.
I have a crew cab long box with spray in liner & tool box loaded down. The worst that I get around town is about 15, and on the road I realistically get about 20 (but have gotten higher).
My average is about 18 on my DIC and my own calculations. And this is with winter fuel.
7500 miles.
GMCTRUCK
03-05-2003, 12:07
That is pretty bad fuel mileage. Even with the 26 gallon tank I got over 400 miles on my very first tank. Sounds like something is out of whack.
I am also looking for fuel around the 370 mi. mark. Big difference in fuel mileage between the 2500's and 3500's !!!!!!!
:eek:
a64pilot
03-05-2003, 13:15
I still find it hard to believe that I am getting 16+ with my cruise on and you guy's are getting 11-12. I'm a CC/LB 3500 as well. Are you guy's up north where they run blended fuel? Down south here I do not believe that the fuel is any thing but straight #2.
I'm in Virginia, so not really what I'd call "The North".
Hmm, sounds like this issue is not unique to my truck. I wonder why there is so much variance between some of our trucks?
P.S. I generally run Amoco 47 Cetane, but sometimes I'm stuck filling up with 45 or even 40 Cetane. Mileage doesn't seem to be affected by where I fill up.
C5Dura
RealBigTruck
03-05-2003, 13:43
That's some nasty mileage! Sounds like something is wrong. Are you consuming oil? If not, I would say the issue is not break-in related.
I just got back from a 700 mile trip from Salt Lake City, UT to the SF Bay empty. I had cruise control on at 80 mph for most of the trip. I averaged 16.8mpg and it's a 2002 3500 (ZF6)with 27k miles. And I don't consider my truck to be very on good fuel. I'll usually get about 300 miles to a tank towing my 24ft enclosed car hauler at 70mph. Usually around 9-10mpg.
Take it to the stealer and complain.
[ 03-05-2003: Message edited by: RealBigTruck ]</p>
Not consuming any oil.
Just called the stealer and he said that all they can do is check to see if there are any codes. Well, I have Autotap and I know I don't have any codes...
Maybe all try talking to the guy that sold me the truck to see what he has to say.
C5dura
thats some ulgy numbers, for a duramax even if it is a 3500,i do have a 2500 but am getting well over 500 miles on the smaller tank(98l)more like 550 miles, when i am towing and pulling heavy weights millage will drop but not under 380 miles a tank
DmaxMaverick
03-05-2003, 15:34
Mileage isn't right. There has to be something really wrong for it to be that bad "just cruising". Get ugly with the dealer!
Fredw:
Change your sig!! That long URL screws up the horizontal size of the page. Either shorten it up, or hyperlink it. Please.
Thanks
WillowCreekStable
03-05-2003, 15:39
Not all 2500's are getting good mileage. I run about 700 miles a week, 70% at 70 mph, 20% at 50 mph, balance around town. It has been cold this winter, but I use the winter front, plug in every night, get in and go, little idling. I check every tank of fuel and I'm consistantly 16 miles per US gallon, plus or minus a tenth or two. That's adjusted for tire size as well. I have 12,000 miles on it. Juice on or off, no measurable difference.
Not complaining, my last gasser was 11-12 mpg. I do wonder how these guys get high teens or 20 though.
Rebel_Horseman
03-05-2003, 15:47
Ditto what WillowCreek said. Around town I'm getting about 14 or 15. I ran to Birmingham, AL at 80+ and got 15 or maybe a little more. Towing at 65 (22+5 flatbed with dual 7,000# single-wheel axles) I got 14.5! Towing a full load of hay I got 8.5 (before I got the Juice). I've never ran the truck at regular hwy speds but I'll know that number this weekend cause I'm going to Houston. Never seen 18 but I'm hoping.
Reb [><]
technician
03-05-2003, 15:52
I dunno... I'm getting about 11.5 - 12.5 I do weigh up a bit though #10,000 constant. Mileage goes up to 14.0- 15.0 on highway w/cruise.
Only thing I can think of is the 235's maybe extra rubber on road ???
Could you're speedo be off ? Might be worth checking.
MadDuraMax
03-05-2003, 16:08
c5dura,
I have about the same mileage on my truck. The first couple of tanks were at just over 15 mpg, now I'm averaging about 13.5. I've seen as low as 12.5 recently (idling, winter fuel?). We seem to have similar driving habits.
My gas mileage seems to be directly effected by "average mph" that I calculate from the hour meter. Best mileage was at about 39 avg. mph and worst at 26.
Is your truck a 4x4? I'm running 65psi in the front tires and 50 in the rears. Those could be the only differences that I see.
Mark
Tech, you might be on to something. Since I'm running taller tires, my speedo reads less than actual, and consequently my odometer will show somewhat less that my true milage.
According to BFG's website, my 235/85/16s are 31.8 inches tall.
I think the factory 'off-road' tires are Wrangler AT/S in 215/85/16s. According to their website, those would be 30.6 inches tall.
Circumference is hmm, err, uum pi * r? If so, we have:
31.8/2*3.14 = 49.93
30.6/2*3.14 = 48.04
So it looks like my speedo/odo is low by about 4%.
11.9 MPG + 4% = 12.38 MPG.
That's a little better, but still nowhere near the 15-16 MPG I see some of you are getting.
C5dura
Landscaper
03-05-2003, 16:21
I have a 02 Chevy C3500 Crew Cab ZF/Duramax with 15,000mls. I have documented every fill up and make sure I fill up to the same point every time. I have gotten as high as 18.5 mpg running hwy. My normal was in the 13-14 pulling 5-6k around town. Mabye its the standard tranny but I have gotten good fuel milage until recently.
I now have a funny sound in the motor and am losing mpg. Its going to the dealer next week.
[ 03-05-2003: Message edited by: Landscaper ]</p>
MadDura, yep mine is 4x4. I'm running 65 in the front and 80 in the rear (I hauled a heavy load a while back and my rears were touching until I upped to 80).
C5dura
GM Smitty
03-05-2003, 16:22
I have 25000 miles on mine (2500HD) now, and have yet to see 16-17 mpg. I usually average about 13-14 on every tank...doesn't matter city or highway. I do have 3 toolboxes and a ladder rack which doesn't help, but I know it should be better. I used to complain alot about it, but the truck runs so good, I don't care much anymore. Fuel prices are what I complain about now! :mad:
Gee- I thought the 25 and 35 in front of the goose eggs was the plant the truck was built in or somethin'
:D
stillracing
03-05-2003, 22:47
MY dually gets 12.5 MPG towing. GOOD POWER so I am not complaining yet. I need to make a run empty to check my best mileage.
I thought my low mileage was due to running in the mountains and high elevation. I guess we can all suffer together.
I guess I should consider myself lucky. I have over 21K miles and I am averaging 16.5 in the winter and over 17 in the summer.
I am used to driving a 454 getting 9 to 11 so I am loving this truck.
C5Dura I thought it might be your rubber also but you've considered that......are you driving in the tow/haul mode?
I don't drive in Tow/Haul unless I'm pulling my trailer.
The only other thing I can think of is the fact that my 20 minute commute to work everyday includes passing over the Blue Ridge Mountains, but the peak is only 2,000 feet or so.
C5dura
I've had mine to the dealer a couple times and they found no codes no problems. I've checked to see if I was pumping fuel into the oil, but it's fine too.
Like I said lousey mileage,,runs and pulls great. Perhaps warmer weather and non-winter fuel will help.
I use stanadyne performance formula every fillup.
just an FYI diesel fuel prices around here 189.9! unleaded 159.9,,,30 cents difference.
BassinRVer
03-06-2003, 13:48
thats some ulgy numbers, for a duramax even if it is a 3500,i do have a 2500 but am getting well over 500 miles on the smaller tank(98l)more like 550 miles, when i am towing and pulling heavy weights millage will drop but not under 380 miles a tank"
There is no way that you are getting 550 miles on the smaller tank maybe more like 550 KM. 550 miles on 22 gallons is 25 MPG.
bullet2110
03-06-2003, 14:38
My '03 4x4 crewcab has never seen 15 mpg always 14.6 to 14.9. Always empty and careful to stay below 2000 rpm's. I have 6500 miles on it and have a appointment at the dealer tommorow looking for help. I don't understand why some never get above 15 mpg and others seem to get 20?
If I get any news from the dealer that may help I'll post it.
my 2001 2500HD extended cab averaged 16.8mpg over the 34,000mi that I owned it. My 2003 2500HD crew cab hasn't recorded anything above 16.2 in the 3500 miles that I've owned it. Most of my running is a mixture of running in town and 2 lane highway and unloaded. I have a cap on the box. I have an excel spreadsheet with all the numbers if anyone is interested. The 2001 was riding on Firestones 245-75-R16's and the 2003 come with the same tire but I have switched to 265-75-R16 Coopers. The rolling circumference difference is 3.8% on the odometer and speedo reads 1.8 mph slow(GPS verified)
FWIW
greg
First, I will reiterate:
Do NOT run your tank repeatedly below 1/8 tank! The fuel in the tank is recirculated to cool the electronics of the injection system.
That said, in mix driving, I have been seeing 15-16 mpg and that almost always includes 2-3 hrs of idle time per tank. This is with 265 Michelins at the moment...
svpdiesel
03-07-2003, 10:48
C5DURA, I have a totally stock 03 2500 4x4 ccsb, 6500 total mi. Average fuel economy is 15.9 mpg. @ 37 avg mph. I drive over a 4mile stretch of 10% grade twice a day, empty. Best I've seen is 20.8mpg @ 62 mph avg. on the freeway, worst 11.8 towing in mixed hilly terrain. Being a California truck with EGR and catalytic convertor, I expected worse. There must be a reason for your poor results, even if it doesn't set a code. Fuel line restriction? Tight driveline? Just guessing, but look at everything, cause something is not right.
Kennedy, thanks for the tip on not running below 1/8. I didn't know the fuel was used for cooling the electronics.
I know 'back in the day' when we had steel tanks, it was not good to run a tank down due to condensation concerns.
I don't think I have ever filled this truck until the 'low fuel' light came on. Wonder if that might be part of the problem?
Perhaps its time to change my fuel filter for the first time and start not running below 1/8 all the time?
I did run it out of fuel twice being stuck out around the farm and put a couple of gallons of high-sulfur off road diesel (for the John Deere)in to get me to the Amoco to fill back up.
C5dura
Spoke to my sales rep and he agreed with me that I should be getting 15-16 mpg on the highway running unloaded.
I have an appointment on Tuesday for them to look at my mileage issue when the truck will be in the shop anyway for my never ending ps fluid leak saga (this will be the 4th visit for the same issue).
I'm not very optimistic as I'm sure they will use my 235/85/16 BFGs as an excuse, and perhaps also the fact that they saw my ODBC Autotap cable on a previous visit and immediately assumed I was running some sort of power enhancer which was noted in my file. :mad:
C5Dura
SwampMonster
03-07-2003, 14:27
I have a 2002 Duramax Crew Cab, 4x4, Short bed, and it sees a lot of highway miles. I typically put 1,000 miles per week on this truck and I recently tested it to see how much mileage I could get. Typically I have been getting right at 17 MPG with 160 miles of interstate and 50 miles of back roads each day. All of my numbers are based on running empty (no loads). I usually drive 9-10 mph over the posted limit, but for testings sake I backed my speed down to the speed limit for half of my trips (evening commute). By just doing this and making sure I stayed out of the turbo I was able to make the 20 MPG mark.
Normal driving: 420 miles on the tank, 23 gallons to fill it up.
Reduced speed driving: 425 miles on the tank, 21 gallons to fill up.
Lata
bassinRver: take a look at a post from a week ago (hot juice versus bully-dog), again all numbers are hiway, i am not the only one getting these numbers(imperial gallons keep in mind)
DMAXTODD
03-09-2003, 23:50
Kennedy,
I ran my truck out of fuel once and since it has not started in below 20 degree weather unless plugged in,or you prime it with the pushbutton on the filter. Do you think maybe I damaged something? My truck runs well otherwise. Your exhaust is sounding and holding up well. I have an excel sheet and averaged 16.75 Mpg since new towing and daily driving,highest was 18.9 Mpg.
DmaxCC6spd
03-10-2003, 11:22
I just ran 430 miles on a tank, the 26 gallon tank. I updated my mileage spreadsheet and I'm getting about 17.5 MPG average. The truck has 15500 miles, K&N filter, and JK exhaust. Otherwise stock. My driving consists mostly of "short" trips, some interstate and occasional towing. During the past summer, a 700 pound mower took up residence in the bed. I consider the overall mileage of the truck to be great. The last tank calculated to 19.96 MPG, lets just call it 20.
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