Castroneves held off fellow Acura Ricky Taylor's Wayne Taylor Racing Acura ARX-05 to secure his second straight win in the event, having won with WTR last year, while Tristan Vautier completed the podium in the leading Cadillac entered by JDC-Miller Motorsports.
The MSR Acura in which the team's full season drivers Jarvis and Blomqvist were making their debuts had to fight back from going down a lap in the fourth hour, when Castroneves was forced to the pits by a left-rear puncture.
And as the numerically-dominant Cadillacs fell by the wayside, with both Chip Ganassi Racing machines and the Ally-liveried Action Express Racing example delayed, the race became a four-way scrap for honours between the Cadillacs of JDC-Miller Motorsports and Action Express, and the two Acuras of MSR and WTR.
With Richard Westbrook leading by 20 seconds for JDC-Miller, a full-course yellow was caused by Matt Bell’s AWA LMP3 car dying at Turn 7 with 1hr55m remaining. Just before, in anticipation of the pitlane being closed, both the Acura teams pitted their cars, WTR bringing in Ricky Taylor for a splash-and-dash, while MSR did likewise for Blomqvist.
MSR then also topped off under the caution, too, pitting with Westbrook handing over to Loic Duval, while Action Express pitted Mike Conway.
Taylor pulled away at the restart, and while Duval initially jumped Blomqvist, the Briton soon resumed second before setting his sights on the lead. With 84 minutes to go, Blomqvist side-drafted Taylor to sneak past into the lead, leaving the two-time IMSA champion to fend off Duval and Conway.
Duval started the penultimate round of stops with 68 minutes to go, the first of the Daytona Prototype international cars to make its penultimate stop. Taylor came in next time by, followed by Blomqvist and Conway - with Castroneves and Pipo Derani taking over their respective mounts.
Castroneves held a five second advantage at the front, but when the charging Duval passed Taylor for second with 55 minutes remaining, that gap went down to half a second. Then out came the full course yellow again for Giacomo Altoe spinning and stalling his GTD class TR3 Lamborghini Huracan.
Just before the restart with just under 30 minutes to go, Derani and Duval pitted for an extra splash, leaving Castroneves and Taylor up front in the Acuras. The four-time Indianapolis 500 winner just held onto the lead at the restart, and the two Acuras started to pull a gap as Derani and Duval held each other up with some side-by-side battling on that first green flag lap.
Castroneves came under severe pressure from Taylor with 15 minutes to go as they threaded through the GT traffic, but the four-time Indianapolis 500 winner pulled away to win by three seconds and clinch victory on the 10th anniversary of MSR’s previous triumph with the late Justin Wilson, AJ Allmendinger, Oswaldo Negri and John Pew.
The LMP2 class was won by the DragonSpeed ORECA of Colton Herta, Patricio O'Ward, Devlin de Francesco and Eric Lux after a late pass from the first-named on Louis Deletraz's Tower Motorsport entry.
That yellow with around two hours to go wiped out DragonSpeed’s 28s advantage in the LMP2 class. Herta then came under Deletraz in the identical Tower ORECA, with Mikkel Jensen only four seconds further down in the #52 PR1 Mathiasen Motorsports entry.
Herta’s lead was only 0.8s when he stopped with 63 minutes to go. Tower and PR1 followed suit the next time by, but on new tyres Herta pulled a three second lead over Deletraz until the final yellow again neutralised proceedings.
Following the pitstops under caution, Tower got Deletraz out ahead of Herta, with Jensen resuming in third. Racing Team Nederland were now right back in the fight, thanks to Rinus VeeKay unlapping himself from Herta two stints earlier, and Giedo van der Garde took over the car in fourth.
At the final restart, Herta initially struggled to hold off Jensen, but with his tyres up to temperature he pulled away and soon caught a fuel-saving Deletraz.
With barely 10mins to go, Herta was right in the Tower car’s slipstream and made a seemingly impossible late-brake manoeuvre into the Le Mans chicane, leaving Deletraz with nowhere to go but the grass.
That also allowed van de Garde, who had demoted Jensen for third, to take second as Herta held on to win.
The battle for GTD Pro class honours came down to a frantic final lap altercation at the Le Mans chicane between the Pfaff and KCMG Porsche 911 GT3Rs, with Mathieu Jaminet, Matt Campbell and Felipe Nasr emerging victorious for Pfaff Motorsports.
The caution with under two hours remaining came just after the leading duo had pitted. They emerged with Jaminet ahead of ahead of KCMG's Laurens Vanthoor, but temporarily behind the Risi Competizione Ferrari 488 of James Calado. The Briton then pitted under caution, handing over to Alessandro Pier Guidi.
The yellows also allowed the Vasser Sullivan Racing Lexus RC F to close up, and following the restart Jack Hawksworth passed the Ferrari. However Pier Guidi soon got back ahead of the luminous Lexus, but had lost ground to the ferocious Pfaff vs KCMG battle.
The two lead Porsches had just stopped when the yellows flew again with 50 minutes remaining, helping them to remain ahead, the Vasser Sullivan crew performing a great final stop to get Hawksworth out ahead of Pier Guidi.
However, the 488 driver wouldn’t let go of the RC F and with 13 minutes to go, the scarlet machine moved back into third, albeit seven seconds behind an increasingly fraught battle for the lead between Jaminet and Vanthoor. The Belgian forced his way by with four minutes remaining after some panel rubbing, but they remained locked together and Jaminet got back ahead on the final lap.
Vanthoor attempted a final move approaching the Le Mans chicane where the two came together, sending the KCMG car spinning across the grass as Jaminet continued on to win with Matt Campbell and Felipe Nasr. By the time Vanthoor rejoined, he had been passed by Pier Guidi, who took second with Calado, Daniel Serra and Davide Rigon, while Vanthoor, Patrick Pilet, Dennis Olsen and Alexandre Imperatori settled for third.
The former GTLM class protagonists BMW Team RLL and Corvette Racing had a difficult race. The best of the new BMW M4 GT3s entered by Team RLL finished 13 laps down in seventh, one spot behind the leading Corvette Racing entry with the de-tuned C8.R.
In the pro-am GTD class, Wright Motorsports ensured a Porsche clean sweep of the GT categories as Zacharie Robichon and Jan Heylen were joined by factory driver Richard Leitz and Ryan Hardwick.
Former Champ Car racer Heylen held off Ferrari factory driver Nicklas Nielsen in the AF Corse Ferrari 488 and Andy Lally's Magnus Racing Aston Martin Vantage at the restart, Nielsen dropping out of second when he was issued a drive-through penalty for making a pass under yellow.
That allowed Lally into second in the Aston Martin he shared with four-time British GT champion Jonny Adam, Spencer Pumpelley and team patron John Potter, while Scott Andrews took third in the Gilbert Korthoff Mercedes AMG GT3.
LMP3 saw Felipe Fraga steer Riley Motorsports to victory by one lap over Sean Creech Motorsports and CORE autosport.
