When your mechanic does not charge you, you want to share the love

On Monday, I brought my car to my car repair and tire shop, McDonough Tire in my hometown of Montclair (New Jersey). The car had stalled on a couple of occasions so I did not want to be stuck on the highway or on one of my concierge runs. I brought the car around noon. It was ready for pickup at 2:15. Nothing major had to be done only some parts in need of cleaning. I went to pick my car around 2:45 pm and when I asked for the Bill, I was told I Owed Nothing. Can you remember ever being told that by your mechanic? Upon reflection, it was a very smart move, since I have used them repeatedly and with that gesture will recommend them to anyone in need of car repairs. Love is the killer App as Tim Sanders said.
Thank you McDonough!