You should always return borrowed items in better shape than you received them.
So the neighbor will receive his truck back a bit cleaner than he lent it and with a full tank of gas.
We’re done with the truck, which means we’ve hauled away the last of the old kitchen. Today we unloaded drywall, wood panelling, rotten subfloor, tired brick molding, and bits and pieces we’d accumulated. The kitchen is stripped and repaired, ready for the new starting Monday with electrical and plumbing. Out with the old. In with the mystery.