Pipo Derani's Extreme Speed Motorsports Nissan DPi led the 12 Hours of Sebring as round two of the IMSA Sportscar Championship passed half distance.
The 2016 Sebring winner ended the first six hours ahead of Ricky Taylor in the #7 Acura Team Penske DPi and the #77 Joest Mazda DPi of Spencer Pigot.
ESM's sole remaining Nissan, which Derani is sharing with Johannes van Overbeek and Nicolas Lapierre, has run consistently in the top three since the start.
It cycled into the lead in the sixth hour during a pit window, and built up a 20-second lead over the competition with Derani behind the wheel.
However, a full course caution at the end of the sixth hour bunched the leaders up and reduced the Nissan's advantage heading into the second half.
Some of the key prototype runners encountered trouble during the opening stanza, including the Wayne Taylor Racing Cadillac which needed to make an extra stop to check water levels.
The #31 Action Express Cadillac also lost time with a penalty for a restart irregularity, but the Felipe Nasr/Mike Conway/Eric Curran driven car has since worked its way back into contention.
ESM's front-row starting Nissan was the day's first retirement, after Olivier Pla spun off at the first corner.
Of the LMP2 contingent, the United Autosports Ligier JSP217 Gibson brought out the race's third caution in hour five when Alex Brundle stopped on-track during a restart.
So far there have been six safety car interventions, including one for an errant gazebo that blew onto the circuit.
Sebring: Positions after six hours
In GTLM, BMW returned to the top of the pile having lost its pole advantage early on, with the Alexander Sims/Bill Auberlen/Connor de Phillippi M8 leading from the Toni Vilander/James Calado/Alessandro Pier Guidi Ferrari 488.
BMW's sister car, which led in the first hour, has since dropped out of contention following contact with the #66 Ganassi Ford GT.
Some of the contenders in GTD have also suffered setbacks, notably the Land Motorsport Audi which led after three hours.
A drive-through penalty from an improperly mounted fire extinguisher cast the Land R8 out of the main battle and off the lead lap.
The #14 Lexus RCF-GT3, meanwhile, lost its place in the top three when its front bodywork came loose, necessitating an extra visit to the pits.
Those incidents helped the cause of the Riley Mercedes-AMG GT3, which led the class at halfway from the Paul Miller Racing Lamborghini.
