Hello and welcome from your neighbor in Mo
Your mileage i cant say what it should be but with my 5th wheel i gross very close to 18000 lbs and i get 7.6 to 8 constantly. Not good but thats what it does
The owners manual is very generic not like your trucks. It shows basic operation such as setting up level and touches on some other things. For more specific information on the appliances you can look them up on line and down load a manual.
If you have questions just ask
Someone on here has been there done that
Just remember the reason you bought it and ENJOY!!