wp_set_post_terms example?

by

Name your fields like car_specs[taxonomy_name], then within “save_post” just do:

foreach($_POST['car_specs'] as $tax => $term)
  if(taxonomy_exists($tax)) // && term_exists($term, $tax)
    wp_set_post_terms($post_id, $term, $tax);

Personally I wouldn’t use WordPress for a auto classifieds type of website. There are PHP frameworks out there better suited for building such sites