Antonio Fuoco claimed the top spot in the three-hour morning session of the Test Day with a 3m30.686s aboard his 499P Le Mans Hypercar, which put him six tenths up on Gustavo Menezes in the best of the Peugeot 9X8 LMHs.
Menezes posted a 3m31.346s, which gave him a margin of just over a tenth over Yifei Ye’s 3m31.477s in the British Jota team’s customer Porsche 963 LMDh.
The second Ferrari ended up fourth on a 3m31.636s set by James Calado.
Toyota, winner of the first three rounds of the WEC this year, could only manage fifth position with a 3m31.856s from Mike Conway in the #7 GR010 HYBRID.
The Briton ended the session with an off at Tertre Rouge which brought out the red flags and a premature end to the session with two minutes left on the clock.
Cadillac took sixth in the times with a 3m32.073s set by Renger van der Zande in the #3 V-Series.R run by Chip Ganassi Racing.
The shake-up in the order established over the first three WEC events of the 2023 season follows revisions to the Balance of Performance revealed last week.
The Toyota has had its minimum weight raised by 37kg, the Ferrari by 24kg, the Cadillac by 11kg and the Porsche by three kilogrammes.
The second cars from Peugeot and Toyota ended up seventh and eighth in the Hypercar times in the hands of Mikkel Jensen and Ryo Hirakawa respectively.
The top 10 in Hypercar was rounded out by the fastest of the factory Penske-run Porsches in which Andre Lotterer ended up on a 3m33.413s and second of the Ganassi cars run under the Cadillac Racing banner in Earl Bamber’s hands.
Glickenhaus Racing was the fastest of the garagistes in the Hypercar class, Olivier Pla taking 11th place in with a 3m34.045s set aboard the best of the team’s Pipo-engined 007 non-hybrid LMHs.
Cool Racing led the way in LMP2 with a 3m36.409s from Reshed de Gerus aboard the fastest of its two ORECA-Gibson 07s.
Paul-Loup Chatin was second quickest in the all-ORECA P2 field for the IDEC Sport team with a 3m37.427s, while Ferdinand Habsburg was third for WRT on 3m37.767s.
The British JMW Motorsport was quickest in GTE Am with its Ferrari 488 GTE Evo with Louis Prette at the wheel.
He posted a 3m56.623s to edge out Ulysse de Pauw in the faster of the AF Corse Ferrari 488 Evos by just over a tenth.
The NASCAR Chevrolet Camaro ZL1, running as the Garage 56 entry, was only slightly slower than the GTE Am pacesetters.
Jenson Button posted the car’s fastest time, a 3m56.880s.
The second three-hour session of the Test Day begins at 15:30 local time.
