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Discussion Starter · #1 ·
Maybe I was expecting too much but I upgraded from an 01 Ford F150 5.4l gas job to a completly stock 07 Classic K2500 crew LBZ expecting better fuel economy then I am getting. When I am towing I have a 19' 4500 lbs (wet) RV.

Running empty @ 68 MPH (110 km/hr) I am getting 13.9 US MPG (16.9 l/100km). Towing @ 62 MPH (100 km/hr) I am getting 10.6 US MPH (22.2 l/100 km)

I was expecting closser to 18-20 US MPH (13 - 12 l/100km) empty and 15 -16 US MPG (15.7 - 14.7 l/100km) towing. Was I way out to lunch? I was getting almost the same economy with my old Ford as I am with the new diesel burner.

I would apreciate feedback from some other duramax owners as to if my expectations were too high or if I may have some engine issues.

Thanks in advance.
 

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When you say completely stock are you still running the 245 tires.
 

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Discussion Starter · #3 ·
Yup, they were just replaced before I bought the truck.
 

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Don't know a whole lot about the the lbz, but I always see a fuel mileage drop when I run the winter fuel blends then usually gain it back when they switch back to summer, but stock my truck only got around 16 maybe 17 it is a lb7 though.....
 

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Are you hand caculating the miles driven by the gallons used. If you are using the DIC, it may not be correct.

My opinion, that is a little below average mileage. Summer fuel will give better mileage.
 

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I have an 06 CC LBZ with 285's. I live just north of Jacksonville, FL. I get around 16MPG in the city and 19 on the interstate. When I have towed (boat or car/dolly) I get around 13-14 on the interstate. But, a diesel is gonna give you torque when climbing hills or grades that the gasser never could.
 

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That is a little on the low side for an LBZ and that light of trailer. But how fast were you going? With that light of a trailer you must have been driving it pretty hard to get that bad of mileage.

First thing to getting good towing mileage, slow down!! Next, depending on how fast you were going, a lot of times you'll get better mileage in 5th gear when towing than in 6th. Did you use Tow/Haul mode?

Lastly, a fresh fuel filter can make a difference in good and poor mileage.

If all else fails, a quality tuner can be good for a mile or two per gallon gain in many situations.

I do think 15-16mpg while towing is very optimistic, and not very realistic, but 12-13 can be obtained with a light trailer and some cautious driving, and good preparation.
 

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Discussion Starter · #8 ·
Thanks to all for the quick replies. Here is a bit of additional info.

I tried towing in both 5th and 6th @ 62 MPH (100 km/hr) and got the same milage which I thought was strange. I think I am due for a filter change and was unaware that it would change the economy.

Also, when does the winter fuel get phased out?
 

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In canada it might be a little while still. When it stips getting cold enough for fuel to gel, then probably another month or so. So it might be a little bit for you northerners. The blended fuel can be as much as 1-2mpg worse.
 

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I have been able to get 21 just cruising around in my 06 LBZ. I have towed 12,000 lbs on a 16 foot gooseneck and saw 12 mpg. thats according to the computer in the truck

oh yeah and i am running 265's
 

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in stock format mpg is gonna suk

u need a chip and exhaust u will see an easy 3-4 mpg gain
 

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I see my best towing mileage at 67mph, locked in 5th. At 62mph, more shifts down to 4th and lower mpg. I don't have anything that light to tow for any true comparisons to yours though.
 

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Tire pressure helps some too. You should bump up your tire pressure to around 65 to 75. I found this helps me alot and keeps them running cooler.
 

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Discussion Starter · #14 ·
Update:
I am not sure if the fuel has changed here in Alberta or the fact I changed my fuel filter but I am now pulling off 17.8 MPG 13.2 l/100km.

Could someone explain to me how changing a fuel filter can help economy? I can see how it can impove performance but not milage.

Thanks for the suggestions
 

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Update:
I am not sure if the fuel has changed here in Alberta or the fact I changed my fuel filter but I am now pulling off 17.8 MPG 13.2 l/100km.

Could someone explain to me how changing a fuel filter can help economy? I can see how it can impove performance but not milage.

Thanks for the suggestions
Hey FG - Always nice to see a fellow cowgarian on board :drink.
I have the exact same truck as you. Your mileage was surprising to even me, and I'm not afraid to say my mileage sucks :rolleyes:.

You're on the right track with the fuel filter. You might also want to replace the air filter if you're not aware of the trucks maintenance history. I wish I could answer your question regarding fuel filter and efficiency gains, but I also find this puzzling. Nonetheless a fresh fuel filter does work wonders.

On another note, I feel like I struck gold recently by playing around with a hand held tuner. If you're prepared to go down that road, I'd be happy to share my experiences with you. ...the economy settings are not always the best settings :rockin

Good luck :cool:
 

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my 03 did a lot better in mileage than my 07. seems to have the same power too
 

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I got 15.5 mpg towing a 5,000 lb horse trailer for 300 miles of the 430 on the tank going 70mph cruise on not in tow mode. With 285 tires, mbrp exhaust, amsoil engine oil, and a topper. Getting 17.6 mpg empty currently. And I keep hearing that the lb7 will get better mileage than my lbz. I can attribute a solid 1/2 mpg increase with the exhaust alone. Good luck.
 
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