Red Bull's Daniel Ricciardo beat Lewis Hamilton's Mercedes to fastest time by just 0.004 seconds in first practice at the German Grand Prix.
The Australian will start from the back of the grid because of engine penalties but team-mate Max Verstappen made it a positive session with third.
Ferrari's Sebastian Vettel was fourth quickest, while using a slower tyre than the two cars in front of him.
Mercedes' Valtteri Bottas was fifth from Ferrari's Kimi Raikkonen.
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- German Grand Prix practice results
It was a low-key session with few incidents, although Raikkonen ran wide at high speed at Turn One, and Renault's Nico Hulkenberg bounced over the grass at the fast Turn 12 on the entry to Hockenheim's famous Stadium section.
And Sauber's Antonio Giovinazzi, driving in first practice in place of regular driver Marcus Ericsson, lost half his engine cover on leaving the pits.
Ferrari's pace might be worrying for Mercedes, as Vettel was only 0.271secs slower despite using the soft tyre, while Red Bull and Mercedes both used the ultra-soft, which is considered to be around 0.5secs quicker.
Raikkonen also used only the soft tyre, but was 0.471secs behind his team-mate.
Vettel starts the weekend eight points clear of Hamilton in the drivers' championship, as the season reaches its halfway point.
Key moves have been made in the driver market this weekend, with Mercedes confirming both its drivers for at least another year. Hamilton has signed a new two-year contract worth up to £40m a year, while Bottas is signed up for 2019, with an option for 2020.
Haas driver Romain Grosjean was seventh and best of the rest, ahead of team-mate Kevin Magnussen and the Sauber of Charles Leclerc, all three powered by the Ferrari engine. Hulkenberg was 10th.
McLaren's Fernando Alonso was 12th after doing very limited running as the team assessed new parts, some for this weekend and some for the subsequent race in Hungary.