Vettel stays on top in second practice
Sebastian Vettel emphasised his morning pace in Singapore by going fastest again in the second free practice session at Marina Bay.
The world champion, who has endured a tough sequence of grand prix weekends in terms of pace recently broken only by his attrition-assisted second place in Belgium, looked rapid throughout Friday.
The second session, which ran entirely under dry conditions, burst into life quickly and it was the two McLarens of Hamilton and Button that set the early pace on the soft tyres.
But just as in the first session, it was Vettel and Hamilton that began trading times at the top of the list.
This continued until Bruno Senna lightly brushed his Williams against the outside wall at Turn 19. The incident may have been small, but the stranded car proved difficult to remove and necessitated a short red-flag period.
When the session resumed, first Massa, and then Hamilton switched to the super-soft option tyre and shot ahead of Vettel and the rest.
The Englishman's 1m49.086s set the tone for what was to follow as the rest of the frontrunners switched to their option programmes.
That prompted Webber to move to the front in the sister Red Bull car, only until Alonso's 1m48.896s bumped the Aussie down. Both were then dropped by Button's 1m48.651, before Vettel settled the matter for good with a 1m48.340s.
The session then settled down into the usual game of cat and mouse as teams tried to evaluate their long run pace while at the same time masking it from their rivals.
Of the frontrunners, Hamilton and Raikkonen both looked rapid on heavy fuel, while Red Bull seemed happy with degradation level of Vettel's super-softs.
Besides Senna's problem, there were no major incidents though once again several drivers rocked over the kerbs at Turn 10 and Perez (15th) ran on at Turn 4 without hitting anything.
The Mexican's Sauber team-mate Kamui Kobayashi (16th) had a similar experience at Turn 1 and then spun at Turn 19 right at the flag drop.