Formula One world champion Sebastian Vettel has wrapped up Chinese Grand Prix practice with another fastest lap for Red Bull ahead of qualifying.
The 23-year-old German, quickest in Friday's two sessions, again topped the timing screens on a grey morning at the Shanghai circuit while Australian team mate Mark Webber struggled to leave the garage.
Vettel's fastest time was one minute 34.968 seconds, 0.208 quicker than McLaren's 2009 world champion Jenson Button who won in China last season.
McLaren's 2008 champion Lewis Hamilton was third with Mercedes' Nico Rosberg fourth.
Webber, who has so far failed to get his title challenge firing on all cylinders, languished in 15th place after spending much of the session in the garage as mechanics swarmed around his car and designer Adrian Newey looked on with a clipboard.
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The Australian appeared to be suffering a recurrence of the KERS (kinetic energy recovery system) problem that dogged him last weekend in Malaysia, and did not set a timed lap until 15 minutes from the end.
Webber ended the session with just five laps completed compared to Vettel's 13.
Champions Red Bull used KERS, the system that gives a brief burst of power at the push of a button, in a race for the first time only last weekend although Webber's system packed up before the start.
Vettel has won the last four races, and first two of the current season from pole position, to lead the championship with a perfect score of 50 points. Button is second overall with 26 while Hamilton and Webber both have 22.
Force India's British rookie Paul Di Resta celebrated his 25th birthday by taking to the track first.
