Nico Rosberg led the way in first free practice for the Austrian Grand Prix, as Formula 1 returned to the renamed Red Bull Ring for the first time in 10 years.
With rain expected to interrupt the later part of the session, both Mercedes drivers made use of the extra set of soft tyres made available to all drivers in FP1 to pump in some early quick laps.
Rosberg set the early pace as Mercedes trialled a titanium skid plate on the floor of the championship leader's car, successfully producing sparks as the German navigated the undulations of the circuit.
An unspecified 'power unit issue' cut short the German's initial running and meant he slipped as low as 13th in the times as other drivers improved, but he returned to the track to set what stood as the fastest time of the session with around 40 minutes to run.
Rosberg's 1m11.295s best put him just over a tenth clear of team-mate Lewis Hamilton, who pushed his Mercedes up to second in between the spells of rain that affected the final 30 minutes of running.
Hamilton had to take evasive action to avoid colliding with his team-mate in the early part of the session, as Rosberg slowed with his engine issue.
Hamilton worked down to a 1m12.255s over an initial 10-lap run, which stood as the benchmark for a long while, until first McLaren's Jenson Button and then Rosberg broke into the 1m11s.
Fernando Alonso looked set to send Ferrari to the top of the times during the opening half-hour, but ran wide after a moment at the penultimate turn and spoiled the lap.
The Spaniard eventually went third fastest, ahead of Felipe Massa's Williams and Button, these three the only other drivers to break through the 1m12s barrier.
The Force Indias of Sergio Perez and Nico Hulkenberg headed the Williams of Valtteri Bottas and the McLaren of Kevin Magnussen, as all eight Mercedes-engined cars occupied the top nine spots on the timesheet.
Jean-Eric Vergne was the fastest Renault-powered runner, rounding out the top 10 for Toro Rosso.
The Frenchman improved in the final five minutes to displace Kimi Raikkonen (also trialling a titanium skid plate on his Ferrari) by just one thousandth of a second.
World champion Sebastian Vettel endured a difficult session on Red Bull owner Dietrich Mateschitz's home circuit, lapping a lowly 15th fastest and narrowly missing the barriers after a wild 720-degree spin across the grass exiting the final turn.
Red Bull team-mate Daniel Ricciardo also survived a wild trip across the grass at the same corner as he battled his way to the 13th fastest time, just behind Toro Rosso rookie Daniil Kvyat and ahead of Sauber's Esteban Gutierrez, who lapped 0.004s faster than Vettel.
Lotus continued to struggle for speed with Romain Grosjean only 16th and failing to escape the 1m13s, while team-mate Pastor Maldonado was 17th quickest, just ahead of both Marussias.
Pos Driver Team Time Gap Laps 1. Nico Rosberg Mercedes 1m11.295s 19 2. Lewis Hamilton Mercedes 1m11.435s +0.140s 32 3. Fernando Alonso Ferrari 1m11.606s +0.311s 23 4. Felipe Massa Williams-Mercedes 1m11.756s +0.461s 27 5. Jenson Button McLaren-Mercedes 1m11.839s +0.544s 33 6. Sergio Perez Force India-Mercedes 1m12.009s +0.714s 33 7. Nico Hulkenberg Force India-Mercedes 1m12.072s +0.777s 20 8. Valtteri Bottas Williams-Mercedes 1m12.114s +0.819s 21 9. Kevin Magnussen McLaren-Mercedes 1m12.313s +1.018s 36 10. Jean-Eric Vergne Toro Rosso-Renault 1m12.364s +1.069s 30 11. Kimi Raikkonen Ferrari 1m12.365s +1.070s 21 12. Daniil Kvyat Toro Rosso-Renault 1m12.372s +1.077s 35 13. Daniel Ricciardo Red Bull-Renault 1m12.570s +1.275s 28 14. Esteban Gutierrez Sauber-Ferrari 1m12.984s +1.689s 19 15. Sebastian Vettel Red Bull-Renault 1m12.988s +1.693s 25 16. Romain Grosjean Lotus-Renault 1m13.168s +1.873s 28 17. Pastor Maldonado Lotus-Renault 1m13.642s +2.347s 27 18. Jules Bianchi Marussia-Ferrari 1m13.738s +2.443s 26 19. Max Chilton Marussia-Ferrari 1m13.857s +2.562s 28 20. Kamui Kobayashi Caterham-Renault 1m14.611s +3.316s 24 21. Adrian Sutil Sauber-Ferrari 1m14.691s +3.396s 9 22. Marcus Ericsson Caterham-Renault 1m17.501s +6.206s 8