SPIELBERG, Austria -- Lewis Hamilton topped the opening practice session for the Austrian Grand Prix as Mercedes track tested its aerodynamic upgrade for the first time.

Hamilton held a 0.127s margin over teammate Valtteri Bottas, who was a further 0.106s clear of Max Verstappen in the Red Bull. Mercedes' advantage was mainly found in the first sector, which is formed of two long straights, but Verstappen had the edge in the high-speed corners of sector two.

Mercedes is running a new aero upgrade this weekend featuring re-profiled sidepods and slots in the rear wing, while Renault is rumoured to have an engine software upgrade capable of unlocking more ultimate performance in the final session of qualifying. First practice suggests the front of the field will be competitive, but it will not be until the final session of qualifying that the true influence of the upgrades becomes clear.

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Sebastian Vettel was fourth fastest for Ferrari, 0.341s off Hamilton, but if recent races have taught us anything it's that the Italian team rarely shows its true hand in Friday practice. Daniel Ricciardo spent a large proportion of the session in the pits after damaging the front-left suspension on his Red Bull on one of the circuit's extreme kerbs. Kimi Raikkonen was sixth fastest in the second Ferrari after locking up and running wide at Turn 3 on one of his fast laps.

Haas' Romain Grosjean was the best of the rest in seventh place after setting his quickest time on the super-soft compound (compared to the ultra-soft used by the top six). Once again, the midfiled looks tightly packed, with Esteban Ocon eighth in the Force India on super-softs, Charles Leclerc ninth in the Sauber on ultra-softs and Pierre Gasly tenth in the updated Toro Rosso on super-softs.

Marcus Ericsson was 11th fastest, underlining Sauber's potential at this circuit, while Kevin Magnussen was 12th after being told he needs to improve in corners one, six and seven to get closer to teammate Grosjean.

Carlos Sainz was 13th fastest in the Renault, which is running a new MGU-K this weekend -- said to be lighter and more reliable than the original one. However, the new component was only fitted to the two works Renaults and Stoffel Vandoorne's McLaren as Fernando Alonso and the two Red Bulls would have suffered a grid penalty after already replacing their MGU-K's at least once this season due to failures.

Sergio Perez was 14th in the second Force India ahead of Nico Hulkenberg, Lance Stroll and Alonso.

McLaren finished the session 17th and 18th as the team continued to run aero tests in order to better understand problems on its car that are not been showing up in the windtunnel. However, the team faced another setback when one of its front wings broke on Vandoorne's car after he ran wide at Turn 10 and clobbered the kerbs. For the record, Alonso was 1.7s off the pace using the soft compound tyre and Stoffel Vandoorne was 1.8s off on the super-softs.

Brendon Hartley was 19th after Toro Rosso back-to-back tested its upgrade on its two cars, with Robert Kubica rounding off the times as he completed the latest of his Friday practice runs for Williams.