.....but just because someone says you need a lens, you only need one if your existing one is not doing something you need
This. So much this.
For cars you want a fairly deep depth of field and you’ll be shooting at f/8 or higher more often than not. Your kit lens performs exceptionally well at small apertures and you won’t see much difference out of a nicer lens.
The biggest secret to good car photos is composition and light. You’d be best served by getting a decent tripod and maybe some off camera flash gear to learn with, in my opinion.