Stephen Simpson paced opening practice in the JDC-Miller Motorpsorts Oreca 07 Gibson in the first on-track session for the IMSA WeatherTech SportsCar Championship ahead of the 65th Mobil 1 Twelve Hours of Sebring on Saturday.

Simpson’s top time of 1:49.516 was set halfway through the hour-long session, and put him just 0.041 seconds clear of Christian Fittipaldi’s No. 5 Action Express Racing Cadillac DPi-V.R which clocked the second fastest time in the Prototype class.

Mike Conway got the sister No. 31 Action Express Cadillac into third, while Jose Gutierrez clocked the fourth fastest lap of practice in the the PR1/Mathiasen Motorsports Ligier JS P217 Gibson.

The pair of Mazdas RT24-P machines driven by Jonathan Bomarito and Joel Miller rounded out the top-six, which was separated by just over 1 second.

Porsche took the top spot in GT Le Mans on the strength of a 1:57.109-lap from Fred Makowiecki with just seven minutes to go in the session in the No. 911 Porsche 911 RSR.

The Frenchman edged the Scott Dixon-driven No. 67 Ford GT by just 0.057 seconds, with Joey Hand in the No. 66 Ford in third.

Paul Miller Racing’s Bryan Sellers was fastest in GT Daytona in his No. 48 Lamborghini Huracan GT3, coming in 0.009 seconds ahead of Lawson Aschenbach in the No. 57 Stevenson Motorsports Audi R8 LMS GT3.

The top four cars in GTD were covered by less than one tenth of a second, with Connor De Phillippi in third for Land Motorsports just 0.074 seconds adrift and Jack Hawksworth in fourth 0.085 seconds behind the class leader in his No. 15 Lexus RC F GT3.

The No. 15 Lexus brought out the session’s only red flag just past the half way mark when Robert Alon pulled the car off course in Turn 10, but it returned to the track to set its fast time later in the practice.

Prototype Challenge saw Pato O’Ward pace the field of four Oreca FLM09 machines, clocking in a session-best time of 1:55.172 in the Rolex 24-winning No. 38 Performance Tech entry.

Up next for the WeatherTech Championship teams is another one-hour practice at 3:15 p.m. ET.

RESULTS: Practice 1