the fuel surcharge is based on $1.20 per gallon,what ever the price of fuel is subtract $1.20.for instance,average price of fuel is $3.42 per gallon,subtract $1.20=$2.22 devide that by if in an E unit, by 6mpg,the fuel suurcharge for a tractor would be $0.37,per every dispatched mile,loaded or empty.thats dead head to pick up,miles the load goes,and dead head too layover.
hope this helps,I dont know what they base the fuel mileage on for the other truck sizes.hope this helps you.