For the umpteenth time this season Mercedes set the pace during PF1 with Lewis Hamilton fastest at Monza, but McLaren were not far behind.
Hamilton will be feeling pretty happy after drawing first blood in his rivalry with team-mate Nico Rosberg ahead of Sunday's Italian Grand Prix - the 2008 World Champion's time of 1:26.187 slotting him in at the top.
While the Mercedes cars were expected to dominate, no one quite predicted McLaren would be so quick, but the MP4-29 showed plenty of promise with Jenson Button splitting the two Mercs to be P2 with a lap that was 0.623s slower than the leading man.
Nico Rosberg had to settle for third with a 1:26.995 with the Ferrari of Fernando Alonso fourth and Button's team-mate Kevin Magnussen completing the top five. They were followed by Sebastian Vettel in the Red Bull and Kimi Raikkonen in the second Ferrari.
In a session that turned out to be pretty straightforward for everyone, the two Williams drivers Valtteri Bottas and Felipe Massa as well as Daniel Ricciardo were "out of position".
Williams, though, rarely show their true pace during FP1 with Bottas slotting in at P12 with a 1:28 and Massa one place behind him. Belgian GP winner Ricciardo didn't have the best of sessions as he first had problems with DRS then ERS and he was down in 16th with a 1218.487.
There were some new faces in FP1 with Roberto Merhi replacing Kamui Kobayashi in the Caterham for FP1 and the Spaniard did an admirable job as his 1:30.704 put him ahead of his team-mate Marcus Ericsson.
Charles Pic got a run at the expense of Romain Grosjean at Lotus, but he was slower than Pastor Maldonado in the sister car while Giedo van der Garde stood in for Adrian Sutil at Sauber.
Dani Juncadella was another who had a taste of the action, but he only took part in the first 30 minutes before making way for Sergio Perez. The Spaniard was P17 with Perez 8.
01 Lewis Hamilton Mercedes 1:26.187 25 laps
02 Jenson Button McLaren +0.623s 27
03 Nico Rosberg Mercedes +0.808s 26
04 Fernando Alonso Ferrari +0.982 23
05 Kevin Magnussen McLaren +1.041s 30
06 Sebastian Vettel Red Bull Racing +1.084s 27
07 Kimi Räikkönen Ferrari +1.306 27
08 Sergio Perez Force India +1.500s 13
09 Daniil Kvyat STR +1.554 33
10 Nico Hulkenberg Force India +1.925s 23
11 Esteban Gutierrez Sauber +1.927s 21
12 Valtteri Bottas Williams- +1.961 20
13 Felipe Massa Williams +1.963 21
14 Jean-Eric Vergne STR +2.113s 30
15 Giedo van der Garde Sauber +2.242s 19
16 Daniel Ricciardo Red Bull Racing +2.300s 12
17 Daniel Juncadella Force India +3.005s 10
18 Pastor Maldonado Lotus +3.325s 24
19 Max Chilton Marussia +3.830s 25
20 Jules Bianchi Marussia +3.894s 27
21 Charles Pic Lotus +3.938s 23
22 Roberto Merhi Caterham +4.517s 23
23 Marcus Ericsson Caterham +4.761s 16
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