Mercedes motorsport chief Toto Wolff has spoken of "the dawn of a new era" on several fronts as the Formula One season starts Sunday with the Australian Grand Prix - without holder Nico Rosberg and ex-F1 boss Bernie Ecclestone but with big rule changes. Rivals led by Ferrari and Red Bull will aim to put the heat on Mercedes immediately in the 20-race campaign which runs over exactly eight months until the November 26 finale in Abu Dhabi.Mercedes won the drivers' and constructors' titles the past three seasons, with Lewis Hamilton prevailing in 2014 and 2015 ahead of team-mate Rosberg before the German turned the tide last year. Rosberg then quit the sport at age 31 a few days later, with Valtteri Bottas moving over from Williams in what Mercedes hope will be an easier partnership with Hamilton than the stormy relationship between Hamilton and Rosberg."We rode the wild horse as best we could. At times we could have reacted differently, perhaps more considerately," Wolff told dpa.Wolff named the new partnership "more relaxed" and said Hamilton had overcome the disappointment of missing a third straight title."I am fitter, I am working harder than ever before, and I am totally focused and ambitious after this last year," Hamilton said.Bottas however does not see himself as a number two driver and ex-world champion Sebastian Vettel also wants to make an early statement with his Ferrari team after a winless 2016 campaign."We are better positioned than last year. We can prove that in Melbourne," said Vettel, who won four straight world titles at Red Bull before Mercedes' dominance.Ferrari gave a first indication of their strength in pre-season testing, while Red Bull with local Australian hero Daniel Ricciardo and Max Verstappen seemingly need to catch up with the two other teams.Friday practice, Saturday qualifying and Sunday's race at Albert Park will also give a first indication of whether the rule changes with now faster cars really make the sport more exciting.Mercedes won 51 of the 59 races in the past three seasons, and a thrilling title race between several teams will help new F1 owners Liberty Media in their bid to make the sport more attractive again - after ending the four-decades reign of the 86-year-old Ecclestone.Bottas' move to Mercedes delayed the retirement of Felipe Massa who now continues at Williams alongside Canadian Lance Stroll, one of two rookies along with Belgium's Stoffel Vandoorne who takes the place of retired ex-champion Jenson Button at McLaren.Mercedes boss Wolff said he and his team are ready for the challenge of maintaining their dominance - having won the Australian race in the past three seasons for a perfect start."We have tackled with determination the challenge of the new regulations. We have been very successful over the last three years through stable rules - but no team has ever maintained its success over such a big regulation change before," he said."In a way, it's just what the doctor ordered. To have such a challenge is good for the team."

Hamilton fastest in 1st practice sessions for Australian GP

Lewis Hamilton has already delivered the faster speeds that Formula One rule changes were designed to achieve, going under the racing lap record during practice Friday for the season-opening Australian Grand Prix. The three-time world champion had the fastest time in morning practice and his afternoon session time of 1 minute, 23.620 seconds was quicker than the racing mark Michael Schumacher set in winning the 2004 title at the 5.303-kilometer (3.295-mile) Albert Park Circuit. It was only one-tenth slower than the best ever lap of Albert Park, which Sebastien Vettel set to take pole position in 2011.

"I'm super happy to be back in the car - particularly after a first day like that. It was 99 percent perfect," Hamilton said. "We've shown good form so far on both the long and short runs and we got every lap done that we wanted to."

Ferrari driver Vettel split the Mercedes cars of Hamilton and Valtteri Bottas, who posted the fastest two times in the opening practice earlier Friday, with his 1:24.167 in the session.