Is it permissible to speak to the dead with words that are not an appeal for help, while being certain that they do not hear, and is saying "Go!" to a car considered major shirk?

Scholars have differed regarding whether the dead can hear, and the more preponderant opinion is that they can hear. Whoever believes that they cannot hear, then his calling out to them and addressing them is futile, not something a sane person would do. One should reflect on ideas before asking about them.