F1: Sebastian Vettel worried, Fernando Alonso very light

From GMM

Shanghai pole sitter Sebastian Vettel has admitted he is concerned about the reliability of his car ahead of Sunday's Chinese grand prix.

Reporters interpreted the German's low tally of laps en route to top spot in qualifying as his "cool" under pressure, but in fact he was concerned about a technical problem.

Both Vettel and Red Bull teammate Mark Webber were grounded with identical differential problems in practice, and the glitch struck again on Vettel's car during the 'Q1' session.

"We were really concerned that the car would not last for the rest of the qualifying, so we agreed on doing basically as little laps as necessary and see if we can manage to get through," he revealed.

Vettel admitted he is now concerned about a recurrence in the race.

"I hope the boys can fix it and I hope it will last," he said.

In the meantime, Fernando Alonso has the lightest car on the grid for Sunday's Chinese grand prix.

The Spaniard, but not his teammate Nelson Piquet, was fitted with a 'double diffuser' for qualifying, and he said qualifying on the front row was "unbelievable".

But when the FIA published the car weights on Saturday evening, it emerged that Alonso's car has just 32 kilograms of fuel on board -- more than 20 kilos less than the Brawns.

The Red Bulls are also quite light: pole sitter Sebastian Vettel is just 8kg heavier than Alonso's car, while Mark Webber is carrying two additional kilos than his teammate.