Lewis Hamilton seized control of the timesheets in FP2 at Spa after a scruffy lap from his team-mate Nico Rosberg.
Although Rosberg set the pace in the morning's first practice for the Belgium GP, his team-mate and main title rival Hamilton came to the fore in the afternoon.
Setting the pace on the medium tyres, the Brit went on to post a 1:49.189 to top the timesheets on the soft tyres.
Rosberg fell 0.604s short as his efforts were undone by a bit of a scruffy lap that included running wide and kicking a bit of gravel onto the track.
Fernando Alonso was third for Ferrari, 0.741s off the pace, while Felipe Massa was fourth ahead of Jenson Button.
Valtteri Bottas brought his Williams home in sixth place in what was a much-improved session for the Grove team. Many are predicting that Williams could be Mercedes' strongest challenger as the weekend unfolds.
Daniil Kvyat finished seventh quickest ahead of Daniel Ricciardo, who notably dropped time on long drag up the hill. He was 1.788s off the pace.
Kevin Magnussen and Nico Hulkenberg completed the top ten.
Pastor Maldonado's session ended on his second lap when he lost his E22, putting it into the barriers at Pouhan.
With a considerable amount of debris on the track - he hit a marker - the session was red flagged to give the marshals a chance to clean up before being restarted five minutes later.
There was also bad news for Sebastian Vettel as his RB10 suffered an electrical problem that necessitated a new engine. He missed FP2.
Meanwhile, Esteban Gutierrez, who sat out FP1 to make space for test driver Giedo van der Garde, completed just seven laps in the afternoon before sliding to a stop at Blanchimont and reporting that something "broke."
01 Lewis Hamilton Mercedes 1:49.189 26 laps
02 Nico Rosberg Mercedes 1:49.793 +0.604 28 laps
03 Fernando Alonso Ferrari 1:49.930 +0.741 19 laps
04 Felipe Massa Williams 1:50.327 +1.138 24 laps
05 Jenson Button McLaren 1:50.659 +1.470 31 laps
06 Valtteri Bottas Williams 1:50.677 +1.488 26 laps
07 Daniil Kvyat Toro Rosso 1:50.725 +1.536 25 laps
08 Daniel Ricciardo Red Bull 1:50.977 +1.788 15 laps
09 Kevin Magnussen McLaren 1:51.074 +1.885 30 laps
10 Nico Hulkenberg Force India 1:51.077 +1.888 26 laps
11 Jean-Eric Vergne Toro Rosso 1:51.383 +2.194 25 laps
12 Adrian Sutil Sauber 1:51.450 +2.261 28 laps
13 Sergio Perez Force India 1:51.573 +2.384 27 laps
14 Romain Grosjean Lotus 1:52.196 +3.007 24 laps
15 Kimi Raikkonen Ferrari 1:52.234 +3.045 18 laps
16 Jules Bianchi Marussia 1:52.776 +3.587 23 laps
17 Esteban Gutierrez Sauber 1:53.955 +4.766 7 laps
18 Max Chilton Marussia 1:54.040 +4.851 17 laps
19 Marcus Ericsson Caterham 1:54.050 +4.861 29 laps
20 Andre Lotterer Caterham 1:54.093 +4.904 24 laps
21 Sebastian Vettel Red Bull No time
22 Pastor Maldonado Lotus No time 2 laps
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