05 duramax
 

Bought this truck a few weeks ago off my FIL. nice truck, runs great. My only complaint is the f'n fuel gauge. Its gotta be off. When it shows empty i can only put aprox 15-16 gallons in it. Truck averages between 10-12mpg pulling my 280 velocity and honestly has more power then i need.

Is this common with the fuel gauge? Its my first diesel but stopping every 170 miles blows. I could go over 200 with my worn out 2000 f150. I would have thought a3/4 ton would go farther then that. Truck has 95k on it and runs great

If memory serves the range is nearly 500 miles per tank. I got almost 13 mpg running 75 mph towing my boat from Dallas to Orange Beach Al., twice. 1260 miles round trip on 2.5 tanks. 05 CC long box 2wd. Your gauge or sender is bad.

Or tank is collapsing .

You could have an issue with the actual gauge cluster too. They are FAMOUS for the stepper motors going out on them. Have you hand calculated your actual fuel mileage?

My 05 CCSB holds around 22-23 gallons, gauge is off I would say

Thanks. Yea its getting roughly 14 driving in town. Bout 11-12 towing on the interstate. Just filled it up tonight. Gauge was at halfway and took exactly 7 gallons. I crawled under the truck and the tank has a sticker that says 26 gallons. I think the gauge must be off

It takes about 4 minutes to pull the gauge cluster out. They are known to go bad, and you can usually find a local automotive electronics shop that can test them for you.

https://www.youtube.com/watch?v=mEVZbaE4aS0

Stepper motors:
https://www.youtube.com/watch?v=mszxIM0UXnE

It should have a 26 gallon tank. I was way low on fuel and put 25.2 into my 2007 Classic CC 2500hd once.

The gauge cluster on my 05 was on the fritz when I traded it in. If you don't want to replace the stepper motors yourself you can get a "reman" cluster from a few places including Jeg's. If you go this route then you need to get it programmed with your mileage information as this is stored in the cluster. Or you can just start again at zero if you never intend on getting rid of the truck.

Side rant: The gauges on my 88 Chevy still work great! They don't make 'em like they used to. Cant wait to see all of the electrical gremlins on my 2016 years from now...

its not the sender, its not the gauge, its the mapping of the fuel sender voltages. usually you can get a dealer to reflash and fix it. or find someone with a tech2 and get it done. just have to re map and make it read somewhat closer to correct. if the stepper motor was bad it would just not work at all. if sender was bad it would flip up and down at random.

I recalibrated mine a few times. It works for a while.

My '08 does the exact same thing. It's empty on the gauge and when I fill it up it only takes 16-17 gallons.

Extremely common problem with those trucks. The only way to truly fix it is pull the tank down and drain it 100% empty. Fill it with 1 gallon at a time and hand populate the table in EFI Live with the readings.