I think I recall reading an article from a few years ago that said J drove a Ford Explorer.
There was also an article that came out between Without A Sound and Hand It Over, that had J interviewed while test driving a car. It might have been Magnet, but I’m not 100% sure. For some reason I think it was a Lincoln Town Car or Continental. From what I recall, it was a cool article, but I’m very biased. If anyone wants more info about that article, I’ll look through my J shrine, and try to dig it up.