This info will be vague at best, but any help would be appreciated. My buddy just got an 03' Quad Cab w/ the 5.9, 3500 w/ 35" tires, 100,000 mi, rebuilt auto trans, beautiful well kept truck. The guy he got it from said he had a Banks kit on it and was getting 19 mpg (assume hwy). The guy took the banks kit off when he sold it and supposedly put it back to stock configuation. My friend just completed a 700 mile trip and got 12 mpg at best w/o towing, and about 8 mpg while towing a small 19' toy hauler, reaching 1100 egt's at times up hills. Egt's were usually around 600 - 700 degrees around town. Said it seemed to have plenty of power and he kept it at 55 - 60 mph. Is this normal for this truck? Based on the info provided, where does a guy w/o deep pockets start looking to better the mpg's, lower the egt's, and get it running like the 5.9's are praised for? I'll pass on any ideas to him. Thanks in advance.

 

A towing performance box that will increase timing a little will help a little.

 

needs to check if correct tire size in ecm, that may throw the mileage out abit.

 

Like 11%.

Change the fuel filter.

 

19 should not be hard to get to with a 5.9, i am almost there with my 6.7, you will need taller than stock tires, a programmer, intake (or high flow filter not k&n), and exhaust