South African driver Stephen Simpson topped the timesheets during the opening practice session for the 12 Hours of Sebring, edging out the quickest of the Cadillac DPi entries in his JDC-Miller Motorsports ORECA LMP2.
Simpson, who shares the car with Misha Goikhberg and Chris Miller, turned in a 1:49.546s time behind the wheel of the #85 ORECA 07-Gibson.
João Barbosa finished the session second quickest, with the #5 Action Express Cadillac DPi winding up just 0.041 seconds off the pace despite a raft of performance-restricting changes following the marque's dominant 1-2 at the Daytona 24 Hours.
Backing up Barbosa's time was the sister #31 Action Express machine driven by Mike Conway, which also lapped within a tenth of a second of Simpson's effort.
Rounding out the top five were the PR1/Mathiasen Motorsport Ligier LMP2 and the #55 Mazda Motorsports DPi.
12 Hours of Sebring FP1 Results
The session was truncated by a brief red flag period just after halfway, following an on-track stoppage for a GTD-class Lexus.
No other major incidents occurred during the hour, although the #70 Mazda DPi did have to return to the pits with a brake fire that was promptly extinguished by mechanics.
In GT Le Mans, Porsche topped the charts thanks to a late flyer by Fréderic Makowiecki in the #911-badged 911 RSR.
The Frenchman's 1:57.109s time eclipsed the second-placed Ford GT of Scott Dixon by 0.057 seconds, with Joey Hand following up closely in the #66 Ford prepared by Chip Ganassi Racing.
Rounding out the top five were the #912 Porsche driven by Laurens Vanthoor, followed by the #68 Ford of Stefan Mücke.
GT Daytona was led by Bryan Sellers in the Paul Miller Racing Lamborghini Huracan GT3, whilst 17-year-old Patricio O'Ward topped Prototype Challenge.
A second free practice session for the 12 Hours of Sebring is bookmarked for 15:15 local time on Thursday.
