The Red Bull family continued its domination of this week's Formula One test in Jerez.
After Toro Rosso's Sebastian Vettel topped the timesheets over the first two days at the southern Spanish circuit, on Thursday it was Mark Webber's turn to lead the way.
The 31-year-old Australian, who will be partnered at Red Bull next season by Vettel, set a best lap time of one minute 19.176 seconds on slick tyres as teams prepare for a return to the rubber for 2009.
Webber edged out Renault's Nelson Piquet into second by 0.158secs, with the Brazilian, who finished runner-up in Sunday's German Grand Prix, also on slick tyres.
For the second successive day Ferrari's Kimi Raikkonen was third fastest on normal grooved tyres, finishing just over a quarter of a second behind Webber.
Force India test driver Vitantonio Liuzzi was fourth as the team continues to successfully trial its seamless shift gearbox this week in readiness to debut at next weekend's Hungarian Grand Prix.
Pedro de la Rosa, who caused one of three red flags by running off at the chicane early on in his McLaren, was down in fifth, followed by Toro Rosso's Sebastien Bourdais and Williams' Kazuki Nakajima.
Timo Glock returned to action following his horrific shunt during Sunday's race at Hockenheim, and after being given the all clear by doctors.
"It was good to get back in the car and that was a positive day's testing for us," said Glock, who was eighth quickest of the 10 drivers on track.
"We pushed hard in the morning and were able to get through most of our plan for the day before lunch."
"The main thing is I've made a full recovery from my accident and I feel fine."
Honda's Rubens Barrichello, who had an engine problem late on, was down in ninth, with BMW Sauber again bringing up the rear with Nick Heidfeld 1.720secs adrift.