I took my truck, 1996 2500 Cummins,6 spd, 11.5 - 3.73 rear, camper top, no trailer to Colorado and back. The fuel mileage was dissapointing 16-16.5 at 70, 15-16 at 80. Is that normal for this truck? The gearing seems to be 1 gear low for my use. I only use 2-4-6 shift. Is there any way to solve this problem short of an OD?

 

i just drove from San Diego to Omaha , then from omaha to Houston , then back to San Diego for the holidays. If i stayed at 65-70 I was getting 20 ish MPG. the big breaking point of these mototrs is once you go past 2k RPMs your mileage drops ALOT.

 

Agreed,

Speed kills fuel mileage. If you keep it a 65 MPH or less, you will see much better mileage. That seems to be right mileage for 70-80 MPH.