Lead generation for cars? Made some progress but looking for more...

I live in Canada and recently started work at a car dealership. One person here has figured out a way to get leads online and apparently does pretty well so I know that this is possible.

I built my own web bot which responds to car ads asking them if they would consider a dealership trade in but the results from this method have been underwhelming (1 / 100 will come in).

Surely I'm not the first person who's wrestled with this problem. What other options are out there?