You can even write off sexy lingerie for your wife if you wear it at least twice while driving the truck. IRS requires of a picture of you wearing it though. Please do not post it to this forum though.
Its a pretty easy simple answer. Any and everything you spend towards operating your business, maintaining your truck, whatever is tax deductible
Even entertainment. ( No not Lot Lizards), But books on tape, Reading material, I would imagine even video games, for off duty time. Work clothes. Mileage from personal vehicle, used for chasing parts, or lease pymt, on a P/U Truck.