Melbourne, Australia - Lewis Hamilton topped the timesheets ahead of new Mercedes team-mate Valtteri Bottas in the first free practice session at the Australian Grand Prix on Friday.
Hamilton clocked a flying lap of 1m24.220s on a warm, cloudy day at Albert Park, more than half a second faster than the Finn in a largely incident-free session.
Red Bull drivers Dan Ricciardo and Max Verstappen were third and fourth fastest respectively, with the Ferraris rounding out the top six.
Hamilton and Bottas posted their fastest laps on the quicker ultra-soft tyres, while other drivers stuck with the super softs, leaving the true pace of the cars unclear.
More definitive was the overall speed of the new cars, many of which were more than four seconds faster per lap compared to the corresponding practice at the 2016 race.
Hamilton's time was less than four-tenths of a second shy of the qualifying lap of 1:23.837 that put him on pole position at Albert Park last year.
Three-times F1 champion Hamilton would have been pleased to put down an early marker ahead of his new team mate Bottas, who replaced retired champion Nico Rosberg.
Ferrari set the pace during winter testing but the 'scuderia' had a subdued session, with Raikkonen edging four-times champion Sebastian Vettel with the fifth fastest lap.
Felipe Massa was seventh fastest for Williams ahead of Haas's Romain Grosjean.
Fernando Alonso was 14th on the time-sheet for Honda-powered McLaren, with his team mate Stoffel Vandoorne at the bottom, underscoring the challenge for the Woking-based outfit after its problems during winter testing.
Briton Jolyon Palmer was 19th out of the 20 cars, his session cut short due to a seal problem with his Renault.Canadian rookie Lance Stroll was 13th for Williams and got through the session unscathed after a number of crashes during winter testing.
2 Valtteri Bottas (Finland) Mercedes - 1:24.803
3 Daniel Ricciardo (Australia) Red Bull - 1:24.886\
4 Max Verstappen (Netherlands) Red Bull – 1:25.246
5 Kimi Raikkonen (Finland) Ferrari - 1:25.372
6 Sebastian Vettel (Germany) Ferrari - 1:25.464
7 Felipe Massa (Brazil) Williams - 1 1:26.142
8 Romain Grosjean (France) Haas – 1:26.168
9 Nico Hulkenberg (Germany) Renault - 1:26.183
10 Sergio Perez (Mexico) Force India – 1:26.276
11 Carlos Sainz (Spain) Toro Rosso – 1:26.450
12 Daniil Kvyat (Russia) Toro Rosso – 1:26.514
13 Lance Stroll (Canada) Williams - 1:26.734
14 Fernando Alonso (Spain) McLaren - 1:27.116
15 Marcus Ericsson (Sweden) Sauber – 1:27.348
16 Esteban Ocon (France) Force India – 1:27.656
17 Kevin Magnussen (Denmark) Haas – 1:27.667
18 Pascal Wehrlein (Germany) Sauber – 1:28.539
19 Jolyon Palmer (Britain) Renault 1:28.585
20 Stoffel Vandoorne (Belgium) McLaren 1:28.695