Campos Racing driver John Filippi set the fastest time in WTCR testing at Barcelona.
Filippi set his fastest lap in the afternoon session, lapping the Spanish Grand Prix circuit in a best time of 1m54.443s in his Cupra TCR with a little more than 10 minutes left on the clock.
He also completed the most laps of any driver, racking up 56 in the four-hour morning and adding 45 to that in the afternoon to surpass the 100-lap mark for the day.
That lap left Filippi more than a second clear of the next fastest car, with Aurelien Panis - the son of 1996 Monaco Grand Prix winner Olivier - beating Comtoyou Racing Audi teammate Nathanael Berthon to second place with a 1m55.452s.
Yann Ehrlacher ended the afternoon session fourth in his Munnich Motorsport Honda Civic, with Frederic Vervisch in a third Comtoyou Audi matching his time of 1m55.782s late on.
Filippi's fastest lap completed an encouraging day for the Campos squad, with him beaten to the fastest time in the morning by teammate Pepe Oriola - who had recorded a 1m54.698s in his Cupra.
That left the Spaniard 0.949 seconds ahead of Filippi, while Berthon was the only other driver in that session to lap within a second of the pace in his Comtoyou Audi RS3 LMS.
Six of the seven brands competing in the WTCR were represented in the top 10 in the morning.
Mehdi Bennani ended up fourth in the morning for the Sebastien Loeb Racing outfit that will benefit from support from Volkswagen Motorsport in 2018, ahead of the two DG Sport Peugeot 308TCRs of Aurelien Comte and Mat'o Homola.
Gabriele Tarquini headed BRC Hyundai teammate Norbert Michelisz for seventh, with Fabrizio Giovanardi (Mulsanne Alfa Romeo) ninth and Vervisch rounding out the morning top 10.
Ehrlacher was also Honda's leading runner in the morning and ended up 12th.
All but one of the season's 25 entries were present, with Rob Huff missing the test and Wednesday's media launch event due to a virus.