I've often sent dealers to non-automotive SEO companies.Precisely Gerry, there's no way that they can scale a quality SEO (and Content Marketing) effort against many thousands of websites. The same can be said of their giant competitors. If your group is doing it because it's coopable, change your strategy (try and move your money elsewhere) and go with a smaller agency. I can point out at least 10 good ones for you.
These companies specialize in diving into new verticals, finding the opportunities and building a unique SEO strategy.
The best part? They think like customers, not like automotive retailers. Big difference.
There are good companies on both sides, but you're more likely to get a unique strategy from someone who isn't representing your competition.