Australian driver Daniel Ricciardo has recorded the third and second fastest times in the two practice session ahead of France’s first grand prix in a decade on Friday.
World champion Lewis Hamilton was fastest on the day for Mercedes.
Hamilton, a point behind Ferrari’s Sebastian Vettel after seven races, complained about his car’s handling over the radio in the first session but still put in a best time of one minute 32.231 seconds. His best time in the second was 1:32.539.
Hamilton’s Finnish team mate Valtteri Bottas, also with a new Mercedes engine in his car, was second fastest in the initial stint but seventh in the second after his car had a water leak.
Ricciardo, winner of two races this season and still mulling his future with his team Red Bull, clocked 1:32.527 and then 1:33.243 later on.
The 90-minute opening session was red-flagged with a minute remaining when Marcus Ericsson lost control at the Beausset corner, spun and hit the barriers hard, with the Sauber car then catching fire.
The Swede worryingly remained in the car, with flames licking the airbox, before marshals arrived with an extinguisher and he clambered out from underneath the halo head-protection system.
Video images later showed extensive scorching to the rear of the car.
Ferrari’s Kimi Raikkonen was fourth on the timesheets in both sessions, with Vettel also fifth in both.
There was further misery for Williams and McLaren, two of the sport’s most successful teams who are going through difficult times, with their drivers filling four of the bottom five places in first practice.
Spain’s double world champion Fernando Alonso, winner at the Le Mans 24 Hours with Toyota last weekend, came down to earth with a bump in 16th place with McLaren team mate Stoffel Vandoorne 19th.
Sunday’s race will be Formula One’s first at Le Castellet’s Paul Ricard circuit since 1990.