Fuel mileage

[the missing link]

Running from Seattle to prince goerge the long way ( dejong) with a low profile step . I am running light but have a 15` wide and 16 ' tall box on the back .I am getting 5.5 loaded and 8 the way back .this is with a 4900 star with a 2250.
My 08 9900 was around 5.5 us pulling super B's .I had better days and way worst days .
The tune is not the end of the world , your right foot is everything .it takes a long time to get used to every trick in the book and to be able to back out .

I am having a very hard time getting this star to hit what my 9900 did .
I still have a few more things to check . Running big heavy loads (9 axel) this truck is running roughly .5 lower loaded and 1 empty less then the 08 9900 driving the same .
Maybe this helps.