For marketing I see QR codes more of a "long tail" tool. With some focus on grabbing the attention of the target audience (headlines) and a well laid out landing page, the conversion could be very good.
The "Scan with Smart Phone to Apply Online" is a perfect example.
This gives me an idea
Look at the demographics of your client base (if you are a franchise dealer this will be readily available). Then match that to the demographic that uses QR codes the most. Put together some catchy headlines and corresponding landing pages with a specific goal in mind.
E.g. Men 35 to 45 for Ford Mustangs: Headline "Do you have what it takes to drive a one? Scan to find out" (Picture of a Mustang with model of course). QR code goes to landing page with a low payment ad and form. Just ask for Name, phone & email (KISS). I am sure there are a lot of ways to create these landing pages, but being a WordPress junkie I know that it is super easy to do using WordPress and Gravity Forms.