This letter praises a dealership or garage for doing good work, finding an elusive problem, etc.
1234, Main Street
Boston, MA 02123
01 April, 2005
<Recipient Address Goes Here>
<date of repair> I brought my <vehicle name, year, etc.> to <location of work> for <kind of repair work>. I was helped by <mechanic name>. I wanted to thank you and congratulate <mechanic name> for doing a wonderful job on my car.
It's all to common to find auto repair businesses that take advantage of their customers and provide subpar service. Thank you very much for being one of the good ones. You've got a customer for life.
encl: <List of enclosed items goes here>