Sergio Perez got the final hour of practice at Le Castellet underway, the Red Bull driver also the first driver to get a provisional time on the board with a 1m33.628s on medium Pirelli tyres.
Perez’s team-mate Max Verstappen also made an uncharacteristic exit after admitting Red Bull had run some experiments in FP2, taking to the track after just a few minutes to try a different set-up.
The reigning world champion immediately took eight tenths off Pérez’s time to take the lead with a 1m32.837s in the middle and then improving to 1m32.808s, just three tenths off Carlos Sainz’s best time in FP2.
Pérez was within half a second of the Dutchman in his second attempt, until Ferrari’s Sainz split the two Red Bulls with a 1m33.217s effort.
Shortly after team-mate Leclerc had faded at the tricky Turn 12, Sainz also had to abort what looked like a possible fastest lap after coming through Beausset’s double right earlier.
Ferrari’s mistakes meant that Verstappen’s time was not challenged until well past the halfway mark.
Mercedes’ Lewis Hamilton briefly held third with a 1m33.255 on softs, a prelude to a flurry of attempts on soft shoes.
Sainz briefly regained second with a lap of 1m33.172s, only to be demoted again by Leclerc’s 1m32.909, still a tenth off Verstappen’s time in the middle.
Sainz, who has to start from the back of the grid after taking a new Ferrari engine, finally overhauled Red Bull in the final 10 minutes thanks to a lap of 1m32.626s, proving fastest in the first and third sector.
But Verstappen responded immediately on his first lap with softs regaining the top for good with an effort of 1m32.272s.
Charles Leclerc, Ferrari F1-75
Photo by: Mark Sutton / Motorsport Images
Sainz and Leclerc finished the session in second and third, three and five tenths down respectively, followed by Hamilton in the Mercedes, the Briton a second off Verstappen’s time.
Perez and Hamilton team-mate George Russell followed in fifth and sixth, ahead of Fernando Alonso, who set a promising seventh time at Alpine’s home race with a late improvement.
Williams’ Alex Albon impressed with an impressive eighth, while Lando Norris once again led the line for McLaren in ninth, with AlphaTauri’s Yuki Tsunoda rounding out the top 10.
The second McLaren of Daniel Ricciardo was 11th, narrowly ahead of the second Williams of Nicholas Latifi.
Lightfi relegated AlphaTauri’s Pierre Gasly to 13th, followed by Alfa Romeo duo Valtteri Bottas and Zhou Guanyu.
Kevin Magnussen, who will also start from the back of the grid with an engine penalty, was 16th in the first Haas, followed by Alpine’s Esteban Ocon.
Aston Martin languished at the bottom with Lance Stroll 18th and Sebastian Vettel last, the pair split by the second Haas of Mick Schumacher, who spent half the session in the garage.
Vettel was unable to complete his final race due to damage to his car, the Aston Martin team tweeted.
F1 French GP: Full FP3 results