Sochi FP1: Hulkenberg fastest after diesel spill delay

A diesel spillage from a cleaning truck forced organisers to shorten Friday's first Russian Grand Prix practice session, with Force India's Nico Hulkenberg eventually ending up fastest.

Mercedes' world champion Lewis Hamilton left it until the last five minutes to set a timed lap and was seventh on the timesheets.

Hulkenberg led a practice session for the first time this season after banging in a quick lap right at the finish, 0.052 quicker than Mercedes' Nico Rosberg, for a best time of one minute 44.355 seconds.

Hamilton's time was of little significance ahead of a weekend that could see his Mercedes team wrap up their second successive constructors' title, and he would have been higher but for a late spin.

The Briton, who leads team mate Rosberg by 48 points with five races remaining, had been second fastest with two minutes to go as the track got quicker.

The 90 minute session was reduced to an hour as workers hosed and cleansed the track following the 'significant' spillage from a truck that had been supposed to sweep the asphalt.

When drivers did go out, on wet tyres, it was on a slippery track with ominous rainclouds replacing the early morning sunshine.

"What a mess," exclaimed Ferrari's Sebastian Vettel, who was third fastest, over the team radio after driving through the affected turns seven and eight.

"It is really slippy," agreed Sauber's Swedish driver Marcus Ericsson.

No time was set for the first 20 minutes before McLaren's Fernando Alonso, who will start from the back of the grid due to penalties for engine changes following a Honda upgrade, got things rolling.

Rain is forecast for the second session.

[highlight ]Russian Grand Prix, Sochi Autodrom - Free Practice 1[/highlight]