My last radio job, where I worked part-time, fired all but one of the part-timers in January 2009 when the Great Recession was raging. One of the big reasons for that bloodletting was the two local auto dealers closed down. If you were a regular listener to the station before the local GM dealer shut down, you would've sworn it owned the station it was on so often. It easily dropped six figures a year on us. About six months later, it returned as a DU (dealer used). I don't know if it ever started advertising on the station again, but I doubt it spent the money it used to spend. All the weekenders except one person who was retired and made his living on eBay had other jobs that paid better than full-time radio. So, the station let us go and kept the full-timers.
At the time, my "real" job was working in IT for a company that worked in vehicles and with car dealers and manufacturers. We had always known that there were two or three times more Ford, GM, and Chrysler dealerships than the market really needed. When the Great Recession hit, we found there were actually six to eight times more of those dealerships than the market needed. With about 1/6 the number of new car dealers as there was 20 years ago, auto isn't nearly the business it once was, and, while most of the remaining dealerships still use radio, most markets just don't have enough of them today for them to support local radio like they once did. Some of those markets have added DU's since the new car dealers closed, but those typically spend less on advertising and are concentrated on smaller areas. There are a few exceptions, but the DU's are generally single market sellers while new car dealers tend to be more regional. Most of the new car dealers where I live today are owned by the McLarty Auto Group (though many of them kept their original names before McLarty bought them), which is based out of Little Rock, AR and has dealerships in at least three states. Very few DU's have a reach anywhere near that.