One way to track how your ads work is to create multiple 'landing' pages on your auto repair shop website each offering a unique service for each different social media profile. Each landing page must only be accessible from a single social media website profile. Use counts of how many people visit each landing page as a measure of the effectiveness of your different offers on different social media websites. Use customer requests for the 'special' service as a measure of how well your offer sells.
Hope this helps