One of the keys to being a small, local business and succeeding on social media is understanding that your is to create a large following relative to the size of the area you're selling to.
You're a mechanic. A fairly common business, so assume that most people would be willing to drive up to 10 miles to go to a shop with a good reputation before they start looking for something closer.
Let's say within that 10 mile radius 30 thousand people are on Facebook. A penetration of 1% of that number, or 300 followers, is enough to be viable and 10% can make a huge difference in the perception of your business, especially when considering that most mechanics within that area aren't working hard to create a positive social presence.
Will 3000 follower take some time to achieve? Yes, especially considering most people aren't on social media to follow car mechanics. A business like this will have a lot of persuading and demonstration of value to do, but it can be done and could make a potentially huge difference in both reputation and reach.
photo taken and Detroit Pianoworks