Germany's defending world champion Sebastian Vettel topped the times as Red Bull dominated Friday afternoon's second free practice session ahead of Sunday's Belgian Grand Prix.
The newly bleach-haired Vettel, who suffered a late puncture, clocked a best lap time of one minute and 49.331seconds to outpace Red Bull team-mate Australian Mark Webber by 0.059 seconds.
Frenchman Romain Grosjean was third quickest for Lotus ahead of Brazilian Felipe Massa of Ferrari as two of the leading teams' number two drivers upstaged their top men in a dry and warm session.
Frenchman Jean-Eric Vergne of Toro Rosso followed suit by also outpacing his team-mate Australian Daniel Ricciardo, who finished down in 16th.
Finland's Kimi Raikkonen, still tight-lipped on his future amid rumours about his intentions for 2014, was sixth in the second Lotus ahead of two-time champion Spaniard Fernando Alonso in his Ferrari. Alonso was fastest in a wet morning session earlier in the day.
Mexican Sergio Perez was eighth for McLaren ahead of German Nico Rosberg in the leading Mercedes with Scotland's Paul Di Resta taking 10th spot for Force India.
Englishman Lewis Hamilton, who scored his maiden win for Mercedes at last month's Hungarian Grand Prix, the last before the mid-season European summer break, was 12th while his former team-mate and compatriot Jenson Button finished up 15th for McLaren.
Vettel and Webber were always in control of the session which was run in much improved conditions that saw one accident when Dutchman Geido Van Der Garde crashed into the barriers with 15 minutes remaining in his Caterham. He escaped serious injury.