Now that I’ve seen OP’s context:
If you’re referring to modern day cars, you don’t want the modern Greek word for automobile (autokineton), which is too clunky. Harma, -atos for chariot is OK, but the Modern Greek colloquial term for car is amaxi, which derives from hamaxa “wagon”. So maybe also hamaxanthrope.
The modern generic term for vehicle is ochema, -atos; originally that was a mule-car, and it was what a war car, a harma, was not (horse vs mule). But by post-Classical Greek, it was the generic term; there’s a 2nd century AD inscription translating the praefectus vehiculorum as eparchos ochematon.
Or, I dunno, just Transformer. 🙂