Not sure if Google T&Cs preclude you from using alternate advertising methods. If not, one approach may be to solicit ads from mechanics, car shops, car mainten

Not sure if Google T&Cs preclude you from using alternate advertising methods. If not, one approach may be to solicit ads from mechanics, car shops, car maintenance training schools, etc. and build in some geo-awareness so you serve up ads local to the site visitor. Could be a very high conversion/CTR and be able to charge a nice fee.