Heck yeah an auto-blog can rank in the search engines. I've been looking into this recently as well and I will share with you my general (couple week old) overview of it.
Go get related keywords to a broad term. Say "cars" for this example, go scrape 5,000 keywords related to this term... "mufflers for 1997 ford, cars for sale in vt, tinting car windows" etc. Then plug these into your auto-blog....
It will go out, fetch related content.. Spin it, making it unique.. And create an entire page around each keyword.. So while there's absolutely NO competition for "tinting car windows" (I wish), maybe the only results it's pulling are sites that happen to have all 3 words scattered about the page.. Not in order..
Here comes you.. With the keyword in your title, URL, onpage, in links, etc. Poof. Now you rank for "tinting car windows" and you get what little traffic that word brings.
Mind you, you won't be ranking these pages (without extra effort) for competitive terms, like "cars." But you don't need to worry about that, you have 5,000 keywords and many of them are bound to have very, very low competition. As a result, many of them are destined to rank.
People also do this just for PR. Ever seen one of those shitty blogs that has a bunch of nonsense posts and a PR3-4? Just fill it up with "quality" content (meaning unique pretty much, nothing more) and start building links to it.. Let it sit there and gather PR for a while and come back to throw your back links on it.
Again, this is just my limited understanding of the topic and I'm still learning a lot about it.
