Carlos Sainz led Charles Leclerc at the top of the times on Friday as Ferrari dominated second practice for the French Grand Prix ahead of world championship leader Max Verstappen of Red Bull.
The Ferrari pair swapped fastest laps in a closely-contested session in bright sunshine, Sainz making light of the prospect of a 10-place grid penalty for Sunday's race after taking new power-train components.
The Spaniard, who scored his maiden victory at the British Grand Prix earlier this month, clocked a best lap in one minute and 32.527 seconds to beat his Monegasque team-mate by 0.101seconds.
World champion Verstappen was a competitive third ahead of George Russell and Lewis Hamilton in the two freshly-updated Mercedes and Lando Norris who was sixth for McLaren.
"We have some work to do," said Verstappen. "It is very hard on the tyres here and we needed a few more laps today.
"It is difficult to judge, but the tyres were hot."
Mercedes were not the only top team to bring an updates package to the south of France as both Ferrari and Red Bull were also running revisions, notably to aerodynamics and floors.
But Hamilton, preparing for his landmark 300th Formula One race, was not impressed with the impact of the Silver Arrows' efforts.
"Today, we're in fourth and fifth so that's kind of the region that we'll be fighting for," he said.
"I don't mean that we can't be on the podium, I think we can still be up there.
- Lacking pace 'everywhere' -
"But we're still not as quick as those front guys – and we're a little bit further back than we were in the last race."
Mercedes had hoped to fight at the front on the smooth circuit that suits their car, but instead, said Hamilton, they "have a lot of work to do – a lot of ground to cover."
"The car's not spectacular here, we don't know why, but hopefully overnight we can make a bit of a step," he said, adding that the car lacked pace "everywhere".
Kevin Magnussen was seventh for Haas ahead of Pierre Gasly of AlphaTauri, Daniel Ricciardo in the second McLaren and Sergio Perez, in the second Red Bull.
Perez, who has been unable to maintain his form consistently since winning the Monaco Grand Prix at the end of May, admitted he needs to make progress with his car set-up overnight.
"It’s not how I want it to be," he said.
The session was uninterrupted and largely uneventful as the teams adapted to the heat – the track temperature was 50 degrees and the air 34 degrees – in front of a big holiday crowd.
The circuit is sold out for both Saturday and Sunday, according to the organisers at the Paul Ricard circuit, where the two Alpine drivers set the initial early pace with Fernando Alonso topping Esteban Ocon before Magnussen and then Russell took over until Leclerc arrived.
The reinvigorated Leclerc had been quickest in the first session and was swift to pick up where he left off in the earlier action.
As expected, it was a tight contest and four minutes later Verstappen edged ahead by 0.010 seconds only for Sainz, facing a grid penalty on Sunday, to sweep clear at the top by 0.850 in 1:33.322.
The heat appeared to have a soporific effect on everyone for a short period before Leclerc returned to beat his Ferrari team-mate’s time by 0.186 only for the Spaniard to respond and jump six-tenths clear.
It was clear that Ferrari had found a sweet spot in their car set-up, but Verstappen was close to matching them on soft tyres, the Dutchman moving up to second briefly before Leclerc replaced him.