Here is a great site with lots of free oil change shops. You can also find dry cleaning shops here too. They have some audit available every month too. You never know what you will find when you search at http://www.mymysteryshop.com/
It only takes a minute to register. You can sign-up for free. You should never pay a fee to register with any site. Then, you can start receiving emails of open shops. You will see information for each shop. You can read about the shop requirements, pay, and location before applying. You can always check the job board for shops in your area. They add new shops daily.
Take a minute and you will start seeing available shops in your email before you know it.