ok, I didn't vote earlier, but now I have more information, so I voted NO!

You don't have to give them an excuse other then, no sorry.

If they don't want to spend the money on renting a car, I wonder how they will feel if something happens to YOUR car and they have to pay for it.

A million things can do wrong, from scratching the paint, to a fender bender, to a major crash. And most of these things can be covered with rent-a-car insurance.