Mercedes' George Russell led the way in practice for the Chinese Grand Prix on Friday ahead of teammate Kimi Antonelli, with the at times twitchy-looking McLarens of Lando Norris and Oscar Piastri heading the chasing pack.
Russell, who won the season opener in Melbourne, posted a flying lap of one minute, 32.741 seconds on soft tires and stayed top of the timesheets for most of the only practice session ahead of qualifying for the sprint race around the Shanghai International Circuit.
The Briton's time was 0.120 seconds quicker than Antonelli.
McLaren looked to have a better handle on their Mercedes power unit, after team principal Andrea Stella complained about a lack of engine data from the supplier following the last race in Australia.
Norris was 0.555 seconds down on Russell's time, with Piastri 0.731 behind the Mercedes.
The papaya-colored McLarens looked to be struggling with the sweeping Turn 1, with Piastri running wide around the 30 minute-mark as the rear end of his car stepped out, with his engineer confirming both cars were facing the same issue.
With Ferrari running their innovative "flip-flop" wing on both cars, Charles Leclerc was fifth fastest and 0.858 seconds behind Russell.
Seven-times world champion Lewis Hamilton switched to the soft tire relatively early in the session and while last year's sprint race winner finished 1.388 seconds off the pace, the track had got quicker by the time Mercedes set their fastest laps.
The Briton's Ferrari suffered an early lock up and spin and also made contact with compatriot Norris in the first half of the session when the McLaren driver attempted a pass only for Hamilton to close the gap going into the corner.
The Haas of Ollie Bearman pipped Red Bull's five-times world champion Max Verstappen, who were 1.685 seconds and 1.800 seconds off the pace.
Dutchman Verstappen will be hoping to avoid a similar situation to the rear-axle lockup that caused him to crash in qualifying at last weekend's Melbourne race.
The Racing Bulls car of Arvin Lindlad stopped after 15 minutes, possibly with a power train issue, taking the rookie out of the only practice session ahead of competitive running on a circuit he has not driven before.
The Audis of Nico Hulkenberg and Gabriel Bortoleto enjoyed a strong first run, finishing ninth and 12th ahead of the second Red Bull of Isaac Hadjar in 13th.
Despite high hopes for the season after the regulations reset, Aston Martin continued to struggle for pace with two-time world champion Fernando Alonso 18th and just two-tenths faster than Valteri Bottas's Cadillac, F1's newest entrants.
