Mark Webber [ Images ] kept Red Bull on course for a 14th pole position in as many races this season, when he lapped fastest in final free practice for the Singapore Grand Prix [ Images ] on Saturday.
The Australian lapped the floodlit 5.073-km Marina Bay Circuit in one minute 46.081 seconds on a dry night in the southeast Asian city-state.
German Sebastian Vettel [ Images ], who can become Formule One's youngest double world champion this weekend with five rounds still remaining, was third fastest in 1:46.345, a day after he comfortably topped the timesheets in his Red Bull.
Vettel has converted 10 pole positions into eight wins this season and will again be a favourite in Saturday's qualifying session.
The 24-year-old was almost a second quicker than the field for a majority of the 60-minute session when soft tires were used. The cars looked better matched when they switched to the super-softs.
Two-time Singapore winner Fernando Alonso [ Images ] was fourth-quickest in his Ferrari [ Images ], while McLaren's Lewis Hamilton [ Images ] was the only other driver to dip below 1:47 to round out the top five places.
The Mercedes [ Images ] pair of Nico Rosberg [ Images ] and Michael Schumacher [ Images ] finished sixth and seventh respectively, separated by just 0.006 seconds but well clear of Felipe Massa [ Images ] in the other Ferrari.
Vettel's soft tires lasted 16 laps in practice on Friday with almost no degradation and suppliers Pirelli expect a majority of the teams to adopt a three-stop strategy for Sunday's race.