SINGAPORE - Sebastian Vettel underlined his ambitions for a third straight victory at the Singapore Grand Prix when the Formula 1 frontrunner dominated free practice on Friday in an awesome display of Red Bull strength.Vettel topped the timesheets with 1min44.249sec on the floodlit 5.073-kilometres Marina Bay street circuit far ahead of team mate Mark Webber, who trailed by .604 of a second.Mercedes followed with Nico Rosberg (1.009) and first-seassion leader Lewis Hamilton (1.119), while Vettel's nearest rival in the championship, Fernando Alonso, was sixth (1.442).IN THE LEADVettel commands the standings with 222 points from 12 of 19 races in his bid for a fourth straight world title which he could wrap up two races after Singapore on October 13 in Japan, if all goes his way.He is 53 points clear of Alonso, with a victory worth 25 points. Hamilton is 81 points adrift. Ferrari-bound Kimi Raikkonen of Lotus, eighth of Friday, has a deficit of 88 points on the leader.Vettel and Alonso have two wins each in Singapore, and Hamilton one. Germany's Vettel is coming off two straight wins for a season-leading tally of six top spots.Practice times are not necessarily an indication of a team's strength as the outfits are trying to find the right set-up for qualifying and the race, and drivers are on different fuel loads.But Red Bull also impressed in longer stints Friday with lots of fuel and increasing tyre wear by being consistently faster than the opposition.Sunday's only night race of the season starts at 8pm (2pm South African-time) under the floodlights which are four times brighter than those used to light football stadiums. Saturday qualifying is also under the lights at 11pm GMT (3pm SA-time).2nd Free Practice Session from the F1 Singapore Grand Prix at Marina Bay Street Circuit 1. Sebastian Vettel (Germany) RedBull - Renault 1:44.249 2. Mark Webber (Australia) RedBull - Renault 1:44.853 3. Nico Rosberg (Germany) Mercedes 1:45.258 4. Lewis Hamilton (Britain) Mercedes 1:45.368 5. Romain Grosjean (France) Lotus - Renault 1:45.411 6. Fernando Alonso (Spain) Ferrari 1:45.691 7. Jenson Button (Britain) McLaren 1:45.754 8. Kimi Raikkonen (Finland) Lotus - Renault 1:45.778 9. Adrian Sutil (Germany) Force India - Mercedes 1:46.002 10. Sergio Perez (Mexico) McLaren 1:46.025 11. Daniel Ricciardo (Australia) Toro Rosso - Ferrari 1:46.406 12. Jean-Eric Vergne (France) Toro Rosso - Ferrari 1:46.429 13. Paul Di Resta (Britain) Force India - Mercedes 1:46.606 14. Nico Huelkenberg (Germany) Sauber - Ferrari 1:46.808 15. Felipe Massa (Brazil) Ferrari 1:46.870 16. Esteban Gutierrez (Mexico) Sauber - Ferrari 1:47.287 17. Valtteri Bottas (Finland) Williams - Renault 1:47.434 18. Pastor Maldonado (Venezuela) Williams - Renault 1:47.761 19. Giedo van der Garde (Netherlands) Caterham - Renault 1:49.434 20. Charles Pic (France) Caterham - Renault 1:49.526 21. Max Chilton (Britain) Marussia - Cosworth 1:49.619 22. Jules Bianchi (France) Marussia - Cosworth 1:49.731 Stay with Wheels24 for the 2013 Singapore GP weekend.