Car Demon has a wide variety of PHP constants that can be used to modify functionality.
Over time many of these constants will be turned into settings that can be adjusted on the settings page. In the meantime you can define these in your wp-config.php file right above where it says:
/* That's all, stop editing! Happy blogging. */
CD_RESTRICT_SPECS_MSG if defined it will use the specs’s capability to determine if a visitor can see the specs. This allows you to force visitors to sign up in order to see all the vehicle specs.
To do this you would add the following to your wp-config.php file:
define( 'CD_RESTRICT_SPECS_MSG', 'Register to see specs.' );