Mad Max is back - but is Mel?

Max is back and he's set to be madder than ever - but will Mel Gibson be onboard?

It was 1979 when a fresh-faced Gibson, then aged 21, took the lead in the first Mad Max movie - still the second most profitable motion picture of all time.

Director George Miller says pre-production is well underway for the fourth instalment of the hugely successful franchise.

But he was tight-lipped on whether Gibson was being cast for the movie, titled Mad Max Fury Road.

Miller also wouldn't comment on what sort of budget it will have, other than to say it will be "very big".

But he did say the movie would take the franchise in a new direction.

"I'm still in the middle of casting, despite all the stuff we see on the net and so on. I don't even know who the final cast will be," Miller told reporters in Sydney on Saturday.

"We've been casting fairly furiously over the last six or seven weeks and I've got a lot of actors to see and so no decision has been made."

There's speculation that Aussie actor Sam Worthington may star in the new movie.

Reports suggest Charlize Theron is a shoo-in for one of the lead roles. And Miller also indicated some unknowns could be cast.

Gibson himself was an unknown actor in 1979.

"I didn't want to make another Mad Max but what happened was the story took hold in my brain somewhere, I became obsessed with the story," Miller said.

"I was ready to do the film, we were 11 weeks away from shooting in Namibia, because that's where we found the landscapes, and then the war came and the American dollar collapsed and we couldn't seal it off at that point."

The collapse of filming in Namibia allowed NSW Premier Nathan Rees to lobby Warner Bros to bring the movie to Sydney.

He told reporters on Saturday the movie will give a long-term boost to the Australian film industry and create 540 jobs in the short term.

"Fury Road: great news for jobs, all the trades people that will work on it - obviously the mechanics, the panel beaters but also the cooks and hundreds of other jobs involved," Mr Rees said.

The recent rise of the Australian dollar has had a "significant impact" on the production of the film, Mr Rees said, but it has not dissuaded Warner Bros from shooting in Sydney.

Filming will get underway in the city and in Broken Hill, outback NSW, during August next year.

Miller said he believes Mad Max Fury Road could boost tourism to NSW, with people keen to see the locations where it is filmed.