Enfold Single.php

Hi,
Can you direct me on where the single.php is called and how I could set up a different call so that it would call to single-category.php depending on the category that is posted?

For example:
Say we have a post type called Automobile and another called Automobiles (plural)
and we would like to change the call to the single.php so that:

normal posts would call to single.php
posts with the category/name automobile would call to single-car.php
posts with the category/name automobiles would call to single-cars.php

I am using the child theme so I can create a file to overwrite the one that is used in the main theme.
Thank you.