Blomqvist crossed the finish line 4.1 seconds clear of the #10 Wayne Taylor Racing ARX-06 of Filipe Albuquerque, Ricky Taylor, Brendon Hartley and Louis Deletraz in a nailbiting finish to the 61st running of the Florida endurance classic, which was punctuated by 14 caution periods.
After a long stretch of green-flag running in the morning hours, a series of full-course yellows kept the top four cars – the two Acuras and Chip Ganassi Racing's pair of Cadillac V-LMDhs – separated by just a handful of seconds in the closing stages.
The yellows helped the WTR Acura, which had dropped three laps off the pace in the night to replace an oil filler bracket, back onto the lead lap, and Albuquerque was able to pass both Ganassi Cadillacs to move up from fourth place to second.
However, Blomqvist was unstoppable aboard the MSR Acura after taking over for the final 90 minutes or so, surviving three restarts with his lead intact to deliver a second consecutive Rolex 24 triumph for the team owned by Jim Meyer and founder Michael Shank, and a third in a row for Castroneves.
The two CGR Cadillacs couldn't keep pace with their Acura rivals when it mattered, albeit engaging in a spirited battle of their own for third.
In the end it was the IMSA full-season #01 entry of Sebastien Bourdais, Renger van der Zande and Scott Dixon that came home for the final spot on the podium, followed by the #02 car of Richard Westbrook, Alex Lynn and Earl Bamber that will contest the FIA WEC this season.
Action Express Racing was fifth with its Cadillac driven by Pipo Derani, Alexander Sims and IMSA debutant Jack Aitken, but 12 laps down on the leaders owing to gearbox issues during the night.
BMW brought home the best of its new M Hybrid V8s in sixth, another three laps in arrears. The #24 car shared by Augusto Farfus, Philipp Eng, Marco Wittmann and Colton Herta had already fallen off the lead lap when it was hit by hybrid issues in the morning hours, and then lost further ground due to a brake change.
The sister #25 BMW of Connor De Philippi, Nick Yelloly, Sheldon van der Linde and Herta was the first GTP runner to hit trouble in the opening hour, which required a change of MGU to solve. The car finally finished 131 laps down.
While BMW lacked the pace to contend for victory, Porsche was well in the mix with its pair of new 963s until both cars hit technical issues.
First to fall off the pace was the #7 car of Matt Campbell, Felipe Nasr and Michael Christensen, which lost 35 laps due to a battery change.
The sister #6 car of Nick Tandy, Mathieu Jaminet and Dane Cameron was well in contention until a spin the morning hours for Tandy. Subsequent caution periods allowed the Briton to recover to one lap behind the leaders when the car expired in a cloud of smoke.
Tandy coaxed the car back to the pits on electric power, but the car did not re-emerge and was finally classified 83 laps down.
LMP2: Proton beats APR in photo finish
Proton Competition stole the LMP2 win in a sensational finish, as James Allen's #55 Oreca 07 beat the #04 Crowdstrike Racing by APR machine of Ben Hanley by a scant 0.016s.
Hanley looked like he had done enough to take the win in the car he shared with George Kurtz, Matt McMurry and Esteban Gutierrez when he repelled the #35 TDS Racing machine of Job van Uitert at Turn 1.
But Hanley didn't reckon on a late charge by Allen, who arrived on the tail of the APR machine at the start of the final lap and regrouped after an attempt to pass around the outside at Turn 1 was firmly rebuffed.
Allen stuck close to the tail of his rival and drafted by on the run to the finish to steal the win by the slimmest of margins for himself and teammates Fred Poordad, Francesco Pizzi and Gianmaria Bruni.
AF Corse completed the podium in third with its Oreca driven by Francois Perrodo, Matthieu Vaxiviere, Julien Canal and Nicklas Nielsen ahead of the TDS machine of van Uitert, Josh Pierson, Francois Heriau and Giedo van der Garde.
The #8 Tower Motorsports car shared by IndyCar stars Josef Newgarden and Scott McLaughlin, as well as Kyffin Simpson and John Farano, was fifth and two laps down after suffering a loss of power on the very opening lap of the race that put them eight laps down.
GTD: Mercedes, Aston Martin victorious
GT Daytona honors were split between Mercedes and Aston Martin in the GTD Pro and GTD categories respectively.
First car home was the GTD class-winning #27 Heart of Racing Aston Martin Vantage GT3 of Roman De Angelis, Marco Sorensen, Ian James and Darren Turner, which was locked in battle until the closing stages of the race with the #57 Winward Racing Mercedes-AMG GT3.
The Winward car, rebuilt around a spare chassis after Lucas Auer's crash in practice, was running second in the closing stages when Phillip Ellis hit the barriers exiting Turn 1 - the same point where Auer had his accident - during the restart following the 13th FCY period.
Winward's demise cleared the way for an Aston Martin 1-2 in GTD, as the Magnus Racing car of John Potter, Andy Lally, Spencer Pumpelly and Nicki Thiim beat the Inception Racing McLaren 720S GT3 of Brendan Iribe, Frederik Schandorff, Ollie Millroy and Marvin Kirchhofer to second.
Heart of Racing had looked good for the GTD Pro win at one stage, but the #23 Vantage of Alex Riberas, David Pittard and Ross Gunn lost a wheel in the night due to a rare wheel-hub failure.
That set-up a three-way dice between the #79 WeatherTech Racing Mercedes-AMG GT3, the solo factory Corvette C8.R and the #14 Vasser Sullivan Lexus RC F GT3 heading into the closing stages.
Maro Engel pulled off what turned out to be the race-winning move when he passed the Lexus of Jack Hawksworth into Turn 1, a move that gave the WeatherTech car also driven by Jules Gounon, Dani Juncadella and Cooper MacNeil crucial breathing space going into the closing stages.
Engel finally beat the Corvette shared by Garcia, Jordan Taylor and Tommy Milner by 3.9s, while the #14 Lexus took third, a further seven seconds down.
Fourth in GTD Pro was the Iron Lynx Lamborghini Huracan GT3 Evo2 shared by Romain Grosjean, Andrea Caldarelli, Mirko Bortolotti and Jordan Pepper, which finished on the lead lap but never had the pace of the leading trio.
Porsche and Ferrari also had weekends to forget with their new GT3 models, which struggled with an unfavorable Balance of Performance.
Best of the new 992-type Porsche 911 GT3 Rs was the Pfaff Motorsports example, which finished fifth in GTD Pro and 12th of all the GTD cars, while newcomers Triarsi Competizione was the first Ferrari squad home, 10th in GTD and 15th in the combined GTD Pro/GTD order.
In LMP3, the #17 AWA Duqueine of Anthony Mantella, Wayne Boyd, Nico Varrone and Thomas Merrill survived a race of attrition to claim the win, taking advantage of a lengthy delay for the long-time leader, the #33 Sean Creech Motorsport Ligier, which suffered a gearbox problem.
The car shared by Lance Willsey, Joao Barbosa, Nico Pino and Nolan Siegel finished a distant second in class ahead of the #38 Performance Tech Motorsports Ligier of John De Angelis, Christopher Allen, Connor Bloum and Cameron Shields.
