All perfect praise be to Allaah, the Lord of the worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.
It is the duty of any person who finds a lost car to report it to the authorities concerned so that they could look for its owner and inform him that his car was found. Using this car is prohibited by consensus. If a person takes possession of it with the intention of owning it, he would be considered a thief.
If he uses it or hires it to others without claiming to possess it, he would be transgressing and will bear a sin in both cases. If someone takes it from him by virtue of hiring, selling or borrowing while knowing that it is stolen or lost, this person will also bear a sin. If this object becomes out of order while being used by the one who hired it, they should both guarantee it. The first one should guarantee it because he is the one who allowed the second one to use it, while the second one should guarantee it because he is the one who used it while knowing that the one from whom he took it does not own it.
Allaah Knows best.