Sebastian Buemi put Toyota Gazoo Racing on top in the first free practice session for the 6 Hours of Shanghai.
The Swiss driver led a 1-2 for the Japanese manufacturer with a time of 1:56.241 that was 1.586 seconds quicker than teammate Jose Maria Lopez in the sister Toyota TS050 Hybrid.
SMP Racing’s Jenson Button led most of the drizzly 90-minute session and his time of 2:00.369 looked set to hold out as the best in session until Buemi came through with 10 minutes remaining.
He was swiftly followed by teammate Lopez and Matevos Isaakyan in the No. 17 SMP Racing BR Engineering BR1 AER, who both eclipsed Button’s time.
Isaakyan finished the session third, while Tom Dillmann ran fourth-best in the No. 4 ByKolles Racing ENSO CLM P1/01 NISMO.
Button eventually finished the session down in seventh, behind the two Rebellion R13 Gibsons.
In LMP2, a flurry of late flying laps ended with Jazeman Jaafar topping the class with a time of 2:07.581 in the No. 37 Jackie Chan DC Racing Oreca 07 Gibson.
BMW Team MTEK Fastest in GTE-Pro
GTE-Pro was led by the No. 81 Team MTEK BMW M8 GTE in which Martin Tomczyk turned in a 2:09.830.
Tomczyk erased the long-standing lead time set by Richard Lietz in the No. 91 Porsche 911 RSR by nearly 2.5 seconds, while Aston Martin’s new-generation Vantage lapped third in the hands of Alex Lynn.
The best of the Ford GTs ran fifth behind Porsche’s other car, while the guesting Chevrolet Corvette C7.R ran seventh with a time of 2:13.182.
Charlie Eastwood’s table-topping effort in GTE-Am, meanwhile, made it the second-fastest time of both GTE fields combined.
The TF Sport driver turned in a 2:11.764, almost two seconds faster than the second-best time set by Matt Campbell in the No. 77 Dempsey-Proton Racing Porsche 911 RSR.
Despite persistent light rain, Free Practice 1 passed without incident.
It will be followed by Friday’s second free practice session, which is due to get underway at 3:30 p.m. local time.
RESULTS: Free Practice 1