At the 6,000 mile mark:

Non-synthetic motor oil
8 ounces of Opti-Lube XPD per 40-gallon tank of fuel
No bed cover or other addons.

Just did a run to Texas and back (3,200 miles). Drove the speed limt... ranging from 55mph to 75mph. The last 400 miles, had 500 pounds of bagged corn in the back.

Overal mileage came in at 18mpg for the trip.

I'm pleased.