Is this MPG normal? How can I increase mpg?

Also gabton, what RPM's do you cruise at? Rear end ratio? Transmission type? Those also come to play when dealing with bad mpg

 

Every truck is specced differently its best to look at the sticker that lists the specs on the truck. I am not sure here it is on an International but on freightliners it usually under the fuse box so i would check around that area to find the specs

 

Does the truck smoke a lot? Low on power? Do you run a lot of stop to go routes?

 

By low on power i mean, does it struggle on hills?

 

It depends on what type of cat engine you're running. The displacements are not really far from each other. Check the turbo area for any leaks and have your CAC (charge air cooler) checked as well. What speeds do you typically run at?

 

Try running 65mph and see if that helps you out. You should install a boost gauge a pyro is also a good idea as well. You will thank yourself later when you have those gauges.