I have an 06 5.9 Cummins 3500 with 125,000 miles, I get 13 to 16 mpg at 73 MPH highway. I am not thrilled at this and when I shared this with my friend with a f250 7.3, he raves about the Bully Dog Chip in his. He said it really helped his mileage, but since I am not schooled at the pros and cons of this, I have always relied on keeping it stock, just as the engineers designed it to get the overall best results. It always seems that once you tweak it, something else goes wrong or you have to address another issue such as ( in this case) guages to monitor the engine if some chips are installed. I am not a fiddler and want a reliable truck with minimal maintenance. Thanks for your comments.
John

 

my advice is to keep it bone stock--add on anything you want

 

Is your 3500 a dually? If so, that's a lot of extra weight, increased rolling and wind resistance.

What gears do you have? If you've got 4.10s you could be running the engine a little higher than peak efficiency.


The engineers have to compromise on a lot of fronts. Cost is a killer. Dodge puts crap torque converters in. Some companies spend the money for billet converters from the factory.

 

Program and enjoy

 

scatpac, what chip did you use and how much better was the gas mileage?

John

 

I've run Smarty and now run EFILive, and on the highway I can get 20mpg easily if I try. That's a 503hp tune at the tires BTW, so it runs pretty strong, and it's with heavy 34.5" tires and 20" wheels. Not really aimed at mileage for sure, but it can do it. A dedicated mileage tune that makes less power but changes timing will net, I'd expect, somewhere in the 15-17 range in town, and certainly 20 if not a bit more on the highway (my 03, for instance, gets every bit of 17 in mostly town/some highway; I live 8 miles out of town).

Currently, mixed in my 07 is in the 14 range, but that's with no regard to mileage; I have the power and I'm not afraid to use it (not that I'm out blowing smoke and squealing tires).

I'd have to recommend EFILive; you'll have a FAR cleaner tune than any box tune, and what you would do is talk to your chosen tuner and say you want the best mileage tune you can get; they email it to you, you load it up, and if it's up to your expectations, good. If not, they make some tweaks and you try that one until it's where you want it. You could also get a good tow tune if you needed it, all depends on what you want.