While gaming increasingly permeates many facets of our daily lives, it is also gaining relevance as an in-car experience. However, despite the growing interest in in-car gaming within both research and practice, we lack a structured understanding of the phenomenon's main research fields and prevailing characteristics. Thus, this paper presents the findings of a scoping review of 42 relevant papers on gaming in cars. We identified five emerging research substreams: in-car game prototypes, gaming during automated driving, theoretical considerations for in-car gaming, effects of gaming while driving, and technology enabling in-car gaming. Furthermore, we provide an overview of the research's major characteristics about the game, gaming device, vehicle, and user. We reflect on trends recognized in our review, discuss contradictory results, for instance, regarding safety, and question whether a unique in-car gaming experience may exist. We propose research questions based on identified trends and gaps to guide future HCI research in this field.