MELBOURNE, Australia (AP) -- Mercedes confirmed its status as favorite to win the Formula One season-opening Australian Grand Prix by setting the fastest two times in Friday's practice sessions, with Lewis Hamilton edging his teammate Nico Rosberg.
Hamilton failed to complete a lap in the opening practice session due to a malfunctioning oil pressure sensor that shut down his engine, but recovered to set a time of 1 minute 29.625 seconds in the second session around the Albert Park circuit, 0.157 seconds ahead of Rosberg.
"That was quite satisfying. On one lap the pace was good, and on the long run, as well," Mercedes team principal Toto Wolff said.
He added, however, that Hamilton's early problem meant there is still cause for concern.
"You need to be very careful because it's enough to have a little problem and the race or qualifying could be finished."
Fernando Alonso of Ferrari was fastest in the first session but dropped to third in the second, half a second off Hamilton's time. Kimi Raikkonen was only seventh fastest in his return to the Italian team after suffering some problems, including failing to select first gear when trying a practice start.
"We're still not on top of all the things we need to resolve," Ferrari team principal Stefano Domenicali said. "The negative sides have to be addressed very quickly because the competition is strong and the time available is not very much."
The gaps at the top of the timesheets were reasonably close, which points toward a competitive qualifying session on Saturday and race on Sunday, rather than the Mercedes dominance that many had predicted.
Red Bull's Sebastian Vettel was tipped to struggle in his campaign for a fifth straight drivers' championship due to his team's preseason struggles with Renault's new V6 turbo engine, but he put in an encouraging performance to finish fourth fastest in practice.
Vettel and new teammate Daniel Ricciardo -- who was sixth fastest -- completed a total of 115 laps, which will provide valuable data on the car and engine's performance.
"It's been a very strong first day for us," Red Bull team principal Christian Horner said. "We've had a very difficult preseason with numerous issues so it was refreshing to get some laps in and get a first proper feel for the car.
"We can see there is quite a gap to the Mercedes and the Ferrari, but we are starting to feel what that gap is and by the end of the weekend we will have a clearer idea."
By contrast, fellow Renault-powered teams Lotus and Caterham did very little running due to a succession of technical problems, coupled with some spins into the gravel traps by Lotus drivers Romain Grosjean and Pastor Maldonado.
There has been concern that these two teams, and perhaps others, will sit out Saturday's final practice session to avoid encountering a problem that takes a long time to fix -- as many do with these new complex engines -- and therefore having to miss both qualifying and the race.
Renault deputy managing director Rob White admitted the company was way behind schedule in integrating the complex new powertrains to its four customer teams.
"It's completely unacceptable to come to the first race as relatively unprepared as we are," White said.
McLaren driver Jenson Button was fifth fastest in Friday's practice, while his rookie teammate Kevin Magnussen was ninth.
Williams driver Valtteri Bottas was eighth, four places above his experienced new teammate Felipe Massa in 12th.
Force India's Nico Hulkenberg rounded out the top ten.