If you lived in the area it sounds like a no brainer to me. Give it to them out of fuel and you get a wash, a full tank of fuel and $250. I'm pretty sure none of my neighbors have given me a loaner, fuel and wash and $250 when I let them use my truck.
A loaner doesn't mean rental,since they are a private contractor they probably have their own fleet of loaners, If you bought a PU. Why would you want to drive a car for up to 3 weeks. I use my truck Since it is still under warranty I take it to the dealer for codes. Unlimited mileage has no draw for me.