Former Sauber Formula 1 driver Felipe Nasr paced two of Saturday's three practice sessions at the Daytona 24 Hours pre-event test.
Nasr, driving the #31 Action Express Cadillac DPi-.V.R., posted the fastest lap of all during the middle run with a time of 1:36.973s.
The 25-year-old Brazilian also went quickest in the night session, while Jordan Taylor led the day's first on-track activity in the Cadillac entered by Wayne Taylor Racing.
Taylor's team-mate and IndyCar champion Ryan Hunter-Reay set the day's second quickest time during the second session, but fell shy of Nasr's marker by 0.083 seconds.
Those two efforts bumped the #31 and #10 cars above Friday leader Filipe Albuquerque (#5 Action Express Cadillac) in the accumulated weekend scoring.
Spirit of Daytona's new Cadillac DPi ended Saturday third quickest in the hands of Eddie Cheever III (+0.257s), while Christian Fittipaldi slotted the #5 AXR machine into fourth.
Rounding out the top five was the LMP2-spec Jackie Chan DC Racing/Jota Sport ORECA-Gibson with Alex Brundle behind the wheel (+0.537s).
However, Brundle's exploits in the Le Mans-winning car weren't enough to unseat the CORE Autosport ORECA, which stands as the fastest LMP2 runner of the weekend so far.
Cadillac's Saturday showing means it has topped each of the five 'Roar Before the 24' sessions of 2018, although there were signs of improvement from the other DPi manufacturers, most notably Acura-Penske.
The pair of ARX-05s moved up to seventh and ninth in the overall scoring, with the best of those coming from Juan Pablo Montoya's afternoon flyer which clocked in at six tenths off Nasr's pace.
Fernando Alonso, meanwhile, improved on his Friday marker to end the second day of running on a time of 1:38.072s, placing the McLaren Formula 1 driver 30th in the individual order so far.
RESULT: IMSA Daytona test practice 3
RESULT: IMSA Daytona test practice 4
RESULT: IMSA Daytona test practice 5
In GT Le Mans, Ford displaced Porsche at the top of the class order through a 1:43.798s effort from Sebastien Bourdais during the night run.
The Frenchman's time eclipsed Laurens Vanthoor's Friday benchmark by nine hundredths of a second, as Ford Chip Ganassi Racing's IndyCar stars commanded every session on day two.
Scott Dixon opened the team's account by leading FP1, while Ryan Briscoe set the pace during FP2.
World GT champion Alessandro Pier Guidi moved up to third in the weekend order with a 1:44.122s effort aboard the Risi Competizione Ferrari.
Porsche factory junior Matteo Cairoli set the fastest GT Daytona lap of the day during the morning session, but the 21-year-old Italian's figure was still two hundredths of a second short of Lamborghini driver Rolf Ineichen's Friday flyer.
The 'Roar Before the 24' test concludes on Sunday with two open practice sessions sandwiching a mock qualifying routine that will determine the pit garage order for the race on January 27-28th.
