Australian Grand Prix: Mercedes chief predicts three-way fight for F1 title

Mercedes boss Toto Wolff (centre) says drivers Valtteri Bottas (left) and Lewis Hamilton are "reasonably happy" with the 2018 car

Mercedes F1 boss Toto Wolff expects the new season to be "a three-way fight between us, Ferrari and Red Bull".

The championship begins in Australia on Sunday and Mercedes and driver Lewis Hamilton are hot favourites, but Wolff is cautious about the team's potential.

"Our drivers seem reasonably happy with our car, but it remains to be seen how well it performs driven in anger," he said.

Mercedes are aiming for a fifth consecutive title double.

The German company's record stretches back to 2014 and the introduction of turbo hybrid engines in F1, since when they have won every single drivers' and constructors' championship.

If they repeat the feat this year, it would to equal a record set by Ferrari.

But Wolff said rule changes restricting teams to just three engines for a season - from four last year - meant Mercedes faced new challenges in 2018.

"The reduction in the number of power-unit components means that reliability will again play an important role in 2018," he said.

"Our reliability in testing looked good but we need to be careful to draw any conclusions from that - despite getting some good mileage with the new car in Barcelona, many of its components have not even come close to the life they need to complete during the season."

He added: "We will tackle this new season with the same dedication, team spirit and energy that has made us strong in the past.

"Each of us has the mindset that last year's championships belong in the past; yesterday's trophies don't win today's games. A new season feels like climbing Mount Everest - we've done it successfully in the past, but we're only in the base camp at the moment.

"It will be a tough journey, with the same target, but different challenges to master along the way. We have to give it everything to be successful again this year."

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Hamilton is in contention with Ferrari's Sebastian Vettel to be the first of the current generation of drivers to win a fifth world title - which would make them equal with the Argentine Juan Manuel Fangio, two behind all-time record holder Michael Schumacher.

Hamilton said: "I personally feel stronger (than last year). That's a positive. I don't know where we are in terms of the pack but reliability has been fantastic and the car feels great.

"It's difficult to know until we get to Melbourne. I definitely feel we are moving in a positive direction."

Hamilton's team-mate this year is Finn Valtteri Bottas, who hopes to provide a tougher challenge for the Briton than last year as he seeks to convince the team to extend his contract into 2019.

Bottas admits that in his second season with Mercedes there are "no reasons" for him to lack performance at some races, as he did last year.

"I know the team, I learned a lot last year and it's entirely up to me to perform," he said. "I think for me to secure a long-term relationship with the team I need results, I need performance, week in, week out, I need to be able to challenge Lewis. That's it; it's completely up to me.

"This year I'll need to use everything I've learned in my five years in Formula 1, especially over the last year, and I need consistency.

"Every driver, including my team-mate, will have some tougher weekends, myself too. But I need to be consistent throughout the year, because I wasn't consistent enough last year to fight for the title. That will be possibly the key."