SHANGHAI, China - Lewis Hamilton topped the time sheets ahead of team mate Nico Rosberg as Mercedes regained its dominance through the first free-practice session ahead of the 2015 Chinese Grand Prix on Friday.
Hamilton lapped the 5.451km circuit in 1min39.033, a half-second quicker than Rosberg.
Rival team Ferrari was next quickest: Sebastian Vettel finished the 90-minute session third ahead of team mate Kimi Raikkonen with Mercedes now very aware of the threat posed by the Italian brand.
Mercedes tweeted at the end of the session: "So that's a wrap chapettes and chaps. P1 for Mr Hamilton, P2 for Mr Rosberg. Our Italian friends lurking ominously in P3 and P4."
Vettel scored a shock maiden win for Ferrari at the previous race in Malaysia, benefiting from a bold strategy and searing track temperatures to end Mercedes' eight-race winning streak.
Cooler Shanghai seems to have sent the team back to the role of best-of-the-rest however, with Vettel ending the morning more than a second slower than Hamilton's benchmark despite a late improvement.
Sauber's Felipe Nasr continued the bright start to his rookie season with fifth-quickest, perhaps inspired by the word "Victory" emblazoned on the side of his helmet in Arabic.
ROOKIE SAINZ GOES EIGHTH
The Brazilian came home ahead of Red Bull drivers Daniel Ricciardo and Daniil Kvyat, usinng new brakes after the team changed suppliers for this weekend after struggling in Malaysia.
Carlos Sainz (Toro Rosso) was eighth quickest while Williams, Mercedes' closest challenger at the end of 2014 but now overtaken by Ferrari, kept a low-profile throughout the morning.
Valtteri Bottas was ninth-fastest while Felipe Massa, who spun late in the session, rounded out the Top 10.
McLaren will have been encouraged by its morning's work: the team seems to have again made some minor progress after a troubled start to the season. Jenson Button and Fernando Alonso qualified 17th and 18th in Malaysia before both cars retired during the race.
They had expected their problems to continue in China.
However Button briefly breached the Top 10 before eventually ending the opening morning 13th fastest. Alonso was 17th, a further three-tenths behind in a tight-packed mid-division.
Times from 2015 Shanghai F1 first free practice
1 Lewis Hamilton (Britain) Mercedes 1min39.033
2 Nico Rosberg (Germany) Mercedes 1min39.574
3 Sebastian Vettel (Germany) Ferrari 1min40.157
4 Kimi Raikkonen (Finland) Ferrari 1min40.661
5 Felipe Nasr (Brazil) Sauber - Ferrari 1min41.012
6 Daniel Ricciardo (Australia) Red Bull - Renault 1min41.029
7 Daniil Kvyat (Russia) Red Bull - Renault 1min41.097
8 Carlos Sainz Jr (Spain) Toro Rosso - Renault 1min41.112
9 Valtteri Bottas (Finland) Williams-Mercedes 1min41.303
10 Felipe Massa (Brazil) Williams-Mercedes 1min41.304
11 Pastor Maldonado (Venezuela) Lotus - Mercedes 1min41.335
12 Max Verstappen (Netherlands) Toro Rosso - Renault 1min41.575
13 Jenson Button (Britain) McLaren 1min41.845
14 Marcus Ericsson (Sweden) Sauber - Ferrari 1min41.918
15 Jolyon Palmer (Britain) Lotus - Mercedes 1min41.967
16 Sergio Perez (Mexico) Force India - Mercedes 1min42.141
17 Fernando Alonso (Spain) McLaren 1min42.161
18 Nico Hulkenberg (Germany) Force India - Mercedes 1min42.184
19 Will Stevens (Britain) Marussia - Ferrari 1min45.379
20 Roberto Merhi (Spain) Marussia - Ferrari 1min46.443