Felipe Nasr led the way during qualifying to determine garage positions for the Daytona 24 Hours, as Cadillac locked out the top four positions.
The former Sauber F1 driver turned in a time of 1:35.806s behind the wheel of the #31 Action Express Racing Cadillac DPi-V.R. that also counted as the fastest lap of the Roar testing weekend so far.
Nasr has now topped three of the seven practice sessions held at Daytona International Speedway, with one more left to run on Sunday afternoon.
The quartet of Cadillacs took turns at the top of the timing screens near the end of the 15-minute shootout, although it was Fernando Alonso who set the early fastest lap in the #23 United Autosports Ligier.
However, as the session progressed, the Dallara-based DPi cars moved into the ascendancy with Nasr, Tristan Vautier (Spirit of Daytona), Renger van der Zande (Wayne Taylor Racing) and Filipe Albuquerque (#5 Action Express) all jostling for the favoured garage position at the front of the pit lane.
In the end, it was Nasr's late effort that set the gold standard, two tenths faster than the second-quickest time from Vautier.
Albuquerque finished third, three tenths off the ultimate pace, while Van der Zande completed the block, six tenths down.
Cadillac's closest challenge came from the pair of Acura-Penske DPi cars, which briefly interjected the top three but fell back later in the session.
Dane Cameron rounded out the top five, just over a second shy of Nasr's lead figure, while Ricky Taylor slotted into sixth position.
Pipo Derani was seventh in the best of the ESM-Nissan DPi runners, ahead of Harry Tincknell in the #55 Joest-Mazda DPi.
Ninth in the scoring was Alex Brundle, who set the fastest lap of the LMP2 contingent with his time of 1:27.274s behind the wheel of the #37 Jackie Chan DC/Jota ORECA.
Alonso, meanwhile, ended the session 1.7 seconds off the pace in twelfth.
In GT Le Mans, Ford and Corvette established themselves as pit neighbours for the 24-hours by sharing out the top four positions.
Joey Hand's 1:43.610s marker put a gap of three hundredths of a second between the quickest Ford GT and the lead Corvette C7.R. driven by Oliver Gavin.
Ford-Corvette was also the order in third and fourth, while Alessandro Pier Guidi qualified fifth for the Risi Competizione Ferrari squad.
Fastest lap honours in GT Daytona were claimed by 2017 Blancpain GT Series champion Mirko Bortolotti, driving one of two Grasser Racing Lamborghini Huracans.
