Castroneves posted a 1m48.237s in his Acura ARX-05 DPi early in the one-hour session.

He knocked Spirit of Daytona driver Tristan Vautier off the top spot by a tenth and a half in the first track acton head of Saturday's second round of the IMSA WeatherTech SportsCar Championship.

The Frenchman retained second position with his 1m48.387s aboard his Cadillac DPi-V.R to the end of the session, ending up just 0.28s ahead of Renger van der Zande in the Wayne Taylor Racing Caddy.

Olivier Pla took fourth in the fastest of the Extreme Speed Motorsports Onroak-Nissan DPis with a 1m48.461s, which put him less than a tenth up on Jonathan Bomarito in the best of the Joest-run Mazda RT24-Ps. Pipo Derani took sixth in the second of the ESM Nissans.

The first nine cars, all DPis, were within a second of Castroneves in the Acura.

Fastest of the LMP2 cars in 11th was the Performance Tech Oreca 07 in which Patricio O'Ward posted a 1m49.457s right at the end of the session.

The United Autosports Ligier was 14th-quickest, 2.5s off the pace, with Paul di Resta at the wheel.

Ford fastest in GTLM

Dirk Muller ended up fastest in the GTE Le Mans class aboard his Chip Ganassi Ford GT. His 1m57.567s put him two and a half tenths up on Toni Vilander in the Risi Competizione Ferrari 488 GTE.

Richard Westbrook was just two thousandths behind in the second of the Ganassi Fords.

The GT Daytona category was led by Lawson Aschenbach in the fastest of the Michael Shank Racing Acura NSX GT3s.

A 2m00.337s put him eight hundredths up on Daniel Serra's AF Corse-run Spirit of Race Ferrari 488 GT3.