Custom post types with categories in template

<?php $args = array( 'post_type' => 'cars' ); // How can I add a category-filter to this?
$args = array(
    'tax_query' => array(
        array(
            'taxonomy' => 'Car-Types',
            'field' => 'slug',
            'terms' => 'Audi'
        )
    )
);
$loop = new WP_Query( $args );
while ( $loop->have_posts() ) : $loop->the_post();
    echo '<li>';
    the_title('<h3>', '</h3>');
    the_content();
    echo '</li>';
endwhile; ?>

http://codex.wordpress.org/Class_Reference/WP_Query#Taxonomy_Parameters