Monza, Italy - Mercedes dominated Italian Grand Prix practice on Friday with Valtteri Bottas pipping team-mate Lewis Hamilton for the fastest lap of the day, with Ferrari's Formula One leader Sebastian Vettel best of the rest.
Hamilton was quickest in a cloudy morning session, with a lap of one minute 21.537 seconds and Bottas coming second, but the tables were turned in the afternoon.
The Finn pulled out a 1:21.406 while Hamilton - who will oust Vettel from the championship lead he has held all season if he wins the last European race of the year on Sunday - was 0.056 slower.
Vettel, seven points clear of his British rival, was third in both sessions with the gap closing in the afternoon to just 0.140. He had been more than a second slower in the opening 90 minutes at Ferrari's home track.
Ferrari Kimi Raikkonen was fourth fastest in practice one and two.
The Ferrari fans will take heart that Mercedes also looked strong in Belgian Grand Prix practice at Spa last weekend. Ferrari closed the gap, with Vettel on Hamilton's tail throughout the race.
"I think going into this weekend we need to be fair and say that the track layout suits Mercedes, but the performance that we showed last week gives us hope," Vettel had told reporters on Thursday.
The Red Bull pairing of Daniel Ricciardo and teenager Max Verstappen followed in fifth and sixth places, but both face grid penalties after Saturday's qualifying because of power unit changes.
Verstappen will have a drop of 15 positions while Ricciardo, who finished third in Belgium last weekend, has a 20 place penalty.
In a surprising move up for struggling McLaren, whose Honda engine has been short on both performance and reliability, Stoffel Vandoorne was seventh quickest and Fernando Alonso eight.
Alonso also has a 35-place grid penalty, however, after Honda announced changes to his car’s power unit, which means the former double world champion, whose future at McLaren remains uncertain due to the team’s continuing engine woes, will start at the back of the 20-car grid for the final European race of the season.
'Not great sport'
His chances were limited anyway at Monza’s ‘Temple of Speed’, the fastest circuit on the calendar where engine performance is crucial. Vandoorne suffered a similar fate when he was handed a 65-place penalty for his home race at Spa-Francorchamps last weekend. Such meaningless penalties incurred through no fault of the driver have come increasingly under scrutiny in Formula One with some saying the system has got out of control and must change.
Formula One managing director Ross Brawn said: “If a car breaks down in a race that’s a technical issue and you’ve affected the race, but I think the fans understand that. But when their hero is on the back of the grid because he had to change the engine, that’s not great sport.”
Formula One regulations stipulate that each driver may use no more than four power units during a championship season, with that number due to be reduced to three in 2018.
Each power unit is made up of six separate components - the engine, turbocharger, kinetic energy generator, heat energy generator, energy store, turbocharger and the control electronics.
Grid penalties are imposed if a driver uses more than four of any one of the components during a season. Alonso is now on his fifth ECU, his sixth energy store, his seventh engine and kinetic energy generator, and his ninth turbo and heat energy generator.
1 Lewis Hamilton (Britain) Mercedes - 1m21.537s
2 Valtteri Bottas (Finland) Mercedes - 1:21.972
3 Sebastian Vettel (Germany) Ferrari - 1:22.652
4 Kimi Raikkonen (Finland) Ferrari - 1:22.689
5 Daniel Ricciardo (Australia) Red Bull - 1:22.742
6 Max Verstappen (Netherlands) Red Bull - 1:22.749
7 Sergio Perez (Mexico) Force India - 1:23.317
8 Esteban Ocon (France) Force India - 1:23.400
9 Stoffel Vandoorne (Belgium) McLaren - 1:23.465
10 Felipe Massa (Brazil) Williams - Mercedes - 1:23.561
11 Carlos Sainz Jr (Spain) Toro Rosso - 1:23.680
13 Lance Stroll (Canada) Williams - Mercedes 1:23.991
14 Daniil Kvyat (Russia) Toro Rosso - 1:24.012
15 Fernando Alonso (Spain) McLaren 1:24.015
16 Romain Grosjean (France) Haas - 1:24.079
17 Nico Hulkenberg (Germany) Renault - 1:24.542
18 Jolyon Palmer (Britain) Renault - 1:25.166
19 Pascal Wehrlein (Germany) Sauber - 1:25.223
20 Marcus Ericsson (Sweden) Sauber - 1:25.687
1 Valtteri Bottas (Finland) Mercedes - 1:21.406
2 Lewis Hamilton (Britain) Mercedes - 1:21.462
3 Sebastian Vettel (Germany) Ferrari - 1:21.546
4 Kimi Raikkonen (Finland) Ferrari - 1:21.804
5 Max Verstappen (Netherlands) Red Bull - TAG Heuer 1:22.409
6 Daniel Ricciardo (Australia) Red Bull - TAG Heuer 1:22.752
7 Stoffel Vandoorne (Belgium) McLaren - 1:22.947
8 Fernando Alonso (Spain) McLaren - 1:22.968
9 Esteban Ocon (France) Force India - Mercedes 1:22.977
10 Felipe Massa (Brazil) Williams - 1:22.985
11 Carlos Sainz Jr (Spain) Toro Rosso - 1:23.150
12 Nico Huelkenberg (Germany) Renault - 1:23.272
13 Jolyon Palmer (Britain) Renault - 1:23.317
14 Sergio Perez (Mexico) Force India - 1:23.352
15 Lance Stroll (Canada) Williams - 1:23.403
16 Romain Grosjean (France) Haas - 1:23.567
17 Kevin Magnussen (Denmark) Haas - 1:23.650
18 Daniil Kvyat (Russia) Toro Rosso - Renault 1:24.253
19 Marcus Ericsson (Sweden) Sauber - 1:24.894
20 Pascal Wehrlein (Germany) Sauber - 1:25.295