The #31 Action Express Racing Cadillac DPi-V.R held sway at the front of the 12 Hours of Sebring field as the race hit one quarter distance.
After three hours, Eric Curran led the #22 Nissan DPi of Nicolas Lapierre by eight tenths of a second, with Jordan Taylor third in the Wayne Taylor Racing Cadillac DPi.
Having started fifth with ex-Formula 1 driver Felipe Nasr behind the wheel, the Action Express squad progressed into the top-two during the opening bout of prototype pit stops 20 minutes in.
Another fast stop from the #31 mechanics at the next set of stops elevated Nasr into a seven-second lead during the second hour, with the #7 Team Penske Acura DPi running second.
In between services the pair of Joest-run Mazda DPis took turns to circulate at the front, although the #55 car is due to serve a penalty for contact with one of the JDC-Miller Motorsports ORECA prototypes.
The pole-sitting Spirit of Daytona Racing Cadillac DPi ran fifth at the close of the third hour, behind the Acura squad's lead car driven by Ricky Taylor.
Qualifying leader Tristan Vautier had a scare at the start when he made contact with Olivier Pla's Nissan DPi at the first corner – Pla tried to round the SDR Cadillac to gain an early lead, but a slight touch sent the ESM-entered Nissan into a wild spin that caused terminal damage.
Vautier continued unabated, and has since handed driving duties over to Matt McMurry.
Sebring: Positions after three hours
Round two of the IMSA Sportscar Championship – which doubles up as part of the North American Endurance Cup – has so far seen one safety car intervention, for an incident between Sebastian Saavedra's Ligier and the Ferrari GTD car of Frank Montecalvo.
Saavedra spun exiting the final right-hander and Montecalvo ran into the stricken prototype, causing the Ferrari to overturn on the outside-wall barriers.
Both drivers walked away from the incident, but the Scuderia Corsa Ferrari has been forced to retire from the race.
In GT Le Mans, reigning FIA world GT champion Alessandro Pier Guidi fronted the class pack after three hours in the Risi Competizione Ferrari 488.
Pier Guidi held an eight-second lead over the pair of Porsche 911 RSRs driven by Gianmaria Bruni and Frederick Makowiecki, which in turn had nine seconds over Bill Auberlen in the pole-sitting BMW M8.
BMW Team RLL commanded the opening hour with the sister car started by Jesse Krohn moving to the front after a slow getaway from Auberlen's team-mate Connor de Phillippi.
Krohn slipped into the mid-pack as the GTLM stops unfolded during hour two, with the Risi Ferrari moving to the front in its place.
The advantage in GT Daytona changed during hour two as the Land Motorsport Audi R8 LMS profited from a penalty to the #15 Lexus RCF GT3.
Lexus driver David Heinemeier Hansson was adjudged to have run over an air pipe during a pit stop, drawing a stop-go from the IMSA officials.
That promoted Sheldon van der Linde to the lead, with the second-placed Paul Miller Racing Lamborghini Huracan running seven seconds down.
Both GT class pole-sitters experienced trouble on the opening lap and have since lost ground: the #3 Corvette of Antonio Garcia/Jan Magnussen/Mike Rockenfeller first lost time with a puncture before spending 17 laps in the garage with a battery change, while the #51 Ferrari of Daniel Serra/Paul Dalla Lana/Pedro Lamy/Mathias Lauda also had a left-rear wheel issue shortly after the green flag.
