SEBRING, Fla.  Sebring Intl Raceway basked in warmth Thursday as action got underway for the 73rd edition of the Mobil 1 Twelve Hours of Sebring, the second round of the IMSA WeatherTech SportsCar Championship.

Sporting a special livery celebrating the 50th anniversary of the creation of BMW North America and BMWs victory in the 1975 Sebring 12-hour race, Sheldon van der Linde drove the No. 25 BMW M Team RLL BMW M Hybrid V8 to the days fastest practice lap.

The 25-year-old South African, who is embarking on his first full season of IMSA competition, lapped the historic 3.74-mile Sebring course in 1 minute, 47.884 seconds (124.800 mph) for overall and Grand Touring Prototype (GTP) class honors.

That was a scant 0.114 second quicker than the 1:47.998 (124.668 mph) tour turned in earlier in the 90-minute afternoon session by Tom Blomqvist in the No. 60 Acura Meyer Shank Racing with Curb Agajanian Acura ARX-06.

Unlike the Rolex 24 staged in late January at an unseasonably cold Daytona Intl Speedway, Florida lived up to its moniker as The Sunshine State as 56 cars across four classes stepped up to the challenge of Sebrings notoriously bumpy surface.

For most of the afternoon practice, Blomqvist topped the timing screens in the Acura he is sharing at Sebring with Colin Braun and IndyCar champion Scott Dixon with a substantial 0.852-second cushion over the next fastest GTP entry, the No. 6 Porsche Penske Motorsport Porsche 963 with Matt Campbell behind the wheel.

Then van der Linde put together his session-topping effort with 14 minutes remaining. Any chance of besting the BMW disappeared when Brendan Iribe made hard right-side contact with a tire barrier in Turn 13 to bring out the red flag with less than three minutes left on the clock. Amazingly, Iribe was able to drive his Grand Touring Daytona (GTD) class No. 70 Inception Racing Ferrari 296 GT3 back to the pits.

Sebring and BMW M Motorsport share a very special bond, stated Andreas Roos, Head of BMW M Motorsport. This track has played an outstanding role in our history in North America, which now spans half a century. We are excited for the anniversary weekend, and our goal is to add new milestones to those already displayed on the liveries of our BMW M Hybrid V8s.

Meyer Shank Racing co-owner Mike Shank is searching for his first victory in the Twelve Hours of Sebring. Acura is the defending Sebring winner, with an ARX-06 fielded by Wayne Taylor Racing.

To me, Sebring is always the hardest race of the year, said Shank. The place challenges every person on the team. We had a good test here last month and our team and HRC (Honda Racing Corp. US) continue to bond and integrate very well.

Last year, the Acura won the race, and we anticipate the car and team will be able to perform at a very high level.

The Rolex 24-winning No. 7 Porsche Penske Motorsport Porsche 963 picked up right where it left off in the days first 90-minute practice, with Nick Tandy setting the early benchmark with a 1:48.651 (123.919 mph) lap. That bested the pair of Meyer Shank ARX-06s by less than two tenths of a second, with Nick Yelloly in the No. 93 car ahead of Braun in the No. 60 car.

The opening session was red-flagged three times, the most significant when Danny Formal suffered an off-course excursion in the GTD class No. 45 Wayne Taylor Racing Lamborghini Huracan GT3 EVO2 that caused a 25-minute delay while a guardrail between Turns 1 and 2 was reconstructed.

A shorter stoppage occurred earlier in the session when the No. 6 Porsche 963 stopped on course with an electrical problem during Mathieu Jaminets out lap.

Thursday marked the official IMSA race weekend debut of the No. 23 Aston Martin THOR Team Aston Martin Valkyrie. The unique prototype features a screaming V-12 engine.

Ross Gunn was able to lap within 2.2 seconds of van der Lindes fast time and his co-driver Roman De Angelis pronounced himself satisfied with the cars competitiveness in the early stages of the Aston Martin program.

First time out, BMW, Porsche, and Cadillac all had the kind of growing pains that were going through now, De Angelis said. We need to keep doing what were doing and just keep plugging away. Weve been saying all week that if we can survive Sebring, we can survive anywhere. Hopefully, Saturday is a good day for us where we can keep learning and keep developing.

Nicklas Nielsen turned the fastest lap of the day in the Le Mans Prototype 2 (LMP2) class in the morning session at 1:50.403 (121.952 mph) in the No. 88 AF Corse ORECA LMP2 07.

In the GT classes, Laurin Heinrich was the only driver to break the 2-minute mark with his 1:59.898 (112.295 mph) tour in the GTD PRO class No. 77 AO Racing Rexy Porsche 911 GT3 R (992). The No. 81 DragonSpeed Ferrari 296 GT3 enjoyed a good day in GTD PRO, with Davide Rigon going fastest in the morning practice and Albert Costa guiding the car to second in the afternoon.

Mercedes-AMG set the pace in both sessions in the GTD class, with Indy Dontje taking the honors in the No. 57 Winward Racing car in the morning and Kenton Koch pacing the afternoon in the No. 32 for Korthoff Competition Motors.