Google has added a note to the product structured data help documentation to explain how to specify car markup and still have Product review snippet feature eligibility.

What is new. The note says “currently Car is not supported automatically as a subtype of Product.” You “will need to include both Car and Product types if you would like to attach ratings to it and be eligible for the Search feature,” Google said.

Code example. Google then provided this example in JSON-LD:

Why we care. If you are just using car schema or just using product schema on your car and automobile landing pages, you will want to make sure to use both. If you do not, any review snippets may not show up in the Google search results for your site and web pages.