Billionaire entrepreneur Elon Musk's claims about the self-driving capabilities of his upcoming Tesla vehicles are "full of crap", General Motors' self-driving Tsar says.

Mr Musk claims his upcoming Model 3 has the hardware to allow full-self driving capability, a Holy-Grail automotive technology that is the focus of huge amounts of research, and offers the potential to allow a driver to read, eat, or even sleep during long trips.

Speaking to Australian journalists in Detroit, GM's director of autonomous vehicle integration Scott Miller, rubbished Mr Musk's claims. GM is yet to bring full self-driving capability to a consumer vehicle.

"I think he's full of crap," Mr Miller said.