Nico Hulkenberg topped a shortened first free practice session for the Russian Grand Prix as poor track conditions made things tricky for the teams.
The Force India driver took first place in the dying seconds with a lap of 1:44.355, finishing ahead of Mercedes driver Nico Rosberg, who was just 0.052 seconds behind Hulkenberg.
Sebastian Vettel finished third for Ferrari, albeit over six tenths behind as the track got faster as conditions improved towards the end.
Sergio Perez completed a strong morning for Force India, the Mexican finishing fourth, ahead of the Red Bull of Daniel Ricciardo and the Toro Rosso of Carlos Sainz.
World champion Lewis Hamilton was only seventh quickest after managing just 10 laps.
The session was shortened due to a diesel spill on track, which meant no running was allowed for the first 30 minutes while the circuit was cleaned.
When the action finally kicked off, drivers had to use wet-weather tyres, as the track was wet in several parts due to the water used to clean the diesel.
"What a mess," said Vettel of the track conditions on his out-lap.
The first drivers who ventured out on slick tyres struggled for grip, and no time was set until 20 minutes had passed, as conditions made it impossible to get any significant running done.
Fernando Alonso was the only driver to appear on the timesheets as the session reached the final 30 minutes, only Marcus Ericsson joining the Spaniard in the following 10 minutes as teams found it pointless to run in those conditions.
As if things were not bad enough, it started to rain, although lightly, with some 20 minutes left on the clock.
Jenson Button jumped to the top of the times with a lap nearly three seconds quicker than Alonso with some 16 minutes to go, the Spaniard reducing the gap to just 0.116s moments later.
Alonso then moved back to the top with a 1:49.250 as the action began to intensify in the final minutes of running.
Valtteri Bottas second a new benchmark with a lap of 1:47.959, before Alonso regained P1 once again with a lap a full half second quicker.
The Williams driver fought back on his following lap on soft tyres, but Hulkenberg went a second quicker in the Force India to demote the Finn to second.
Rosberg then moved to second with his first timed lap of the session, set with six minutes left on the clock.
Hamilton took it even easier than his teammate, the world champion not featuring on the timesheets until the final five minutes, when Vettel went quickest with a 1:45.491.
The Ferrari driver went even quicker in the dying moments, setting a new benchmark with a lap of 1:44.986, before he was outpaced by Hulkenberg (1:44.355) and Rosberg (1:44.407).
The session ended with two spins, first by Felipe Massa and the by Hamilton.
|1||Nico Hulkenberg||Force India||1:44.355||11|
|4||Sergio Perez||Force India||1:45.146||+0.791||11|
|5||Daniel Ricciardo||Red Bull Racing||1:45.233||+0.878||10|
|6||Carlos Sainz Jr.||Toro Rosso||1:45.488||+1.133||13|
|9||Max Verstappen||Toro Rosso||1:46.203||+1.848||13|
|15||Pastor Maldonado||Team Lotus||1:48.006||+3.651||9|
|16||Daniil Kvyat||Red Bull Racing||1:48.096||+3.741||9|
|17||Jolyon Palmer||Team Lotus||1:49.094||+4.739||9|