(CNN) -- Sebastian Vettel shows no sign of letting up in his quest for a fourth world title after dominating the second practice session at the Singapore Grand Prix.
The Red Bull driver, who is currently 53 points ahead of Ferrari's Fernando Alonso in the drivers' championship, put in another stellar showing at the Marina Bay Street Circuit on Friday.
Vettel's time of one minute 44.249 seconds was 0.604 seconds faster than teammate Mark Webber as the pair comfortably outpaced Mercedes duo Nico Rosberg (1m 45.258s) and Lewis Hamilton (1m 45.368s).
Hamilton had topped the opening practise session but as dusk fell it was Red Bull who turned up the gas.
"We really made a step forward. The car felt really good -- and if you have confidence in your machine you can take it closer to the walls. Both tyre compounds worked, so I am looking forward to qualifying," Vettel told Formula1.com.
Alonso (1m 45.691s) had to settle for sixth spot behind Lotus' Romain Grosjean (1m 45.411s) with Jenson Button finishing in seventh ahead of Kimi Raikkonen who was eighth fastest.
Force India's Adrian Sutil was ninth while McLaren's Sergio Perez was tenth.
The third and final practice gets underway on Saturday evening ahead of qualifying for Sunday's race.