Sebastian Vettel outpaced Lewis Hamilton to begin an important Chinese GP weekend for himself and Ferrari with a place at the head of the Practice One timesheet.
Having admitted on Thursday that "I can do better" after a problematic beginning to his season, Vettel made a fast start in Shanghai and set the early pace from Mercedes rival Hamilton by 0.207s, despite not using Pirelli's fastest tyres.
Bahrain GP star Charles Leclerc was third in the second Ferrari, close behind Hamilton, and he too stayed on the mediums rather than the quicker soft compound.
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"The Ferrari has the pace we expected," said Sky F1's Martin Brundle after Vettel's leading time of 1:33.911. Mercedes believe the Scuderia's straight-line speed advantage will prove a key strength for their rivals again this weekend.
"It was a frightening lap from Sebastian in terms of straight-line speed, but we have to stretch ourselves and maximise our package," said Mercedes boss Toto Wolff. "Having a benchmark like that helps to motivate."
After repairs and analysis at their Maranello base, Ferrari ran the engine on Leclerc's car which developed the critical problem which cost the youngster a maiden win a fortnight ago at Sakhir. In a further apparant early boost for the Italian team, the unit appeared to run without problem.
Max Verstappen was fourth-fastest for Red Bull, as they continue to dial in their RB15, ahead of championship leader Valtteri Bottas in the second Mercedes.
Daniel Ricciardo, who has yet to score points for Renault, was an encouraging sixth-fastest in the lead RS19 with the French manufacturer introducing intended reliability fixes for their troublesome MGU-K unit this weekend.
Ricciardo's replacement at Red Bull, Pierre Gasly, is still undergoing his own acclimatisation process to a new team and car and the Frenchman was seventh-quickest in P1, just ahead of Toro Rosso's Daniil Kvyat.
After a tough Bahrain, Racing Point could take early encouragement from the timesheet as Lance Stroll finished a promising ninth, ahead of the two Haas cars.
Alfa Romeo have taken an early lead in the midfield battle for fourth place in the Constructors' Championship but they experienced a difficult Friday morning in Shanghai.
An engine installation problem restricted Antonio Giovinazzi to just two untimed laps, while Kimi Raikkonen was just 15th fastest in the other car.
Practice Two begins at 7am, live on Sky Sports F1 and Sky Sports Main Event.
Watch the Chinese GP, F1's 1,000th race, live on Sky Sports F1 this weekend. Sky Sports is the home of live and exclusive F1. Find out more here to watch the 2019 season live