The Action Express Racing Cadillac DPi-V.R of Filipe Albuquerque and Joao Barbosa claimed victory at the Long Beach round of the IMSA Sportscar Championship.
Albuquerque crossed the line 4.766 seconds ahead of Ryan Dalziel in the #22 ESM Nissan DPi to chalk up the second win of the year for Action Express, following its Daytona 24 Hours triumph in January.
The early stages of the 1 hour 45 minute contest had been led by the pole-sitting Acura ARX-05 DPi of Juan Pablo Montoya.
But Team Penske's decision to affix tyres to Montoya's car (later driven by Dane Cameron) for the final stint enabled Albuquerque, who had not taken tyres and therefore saved time, to cycle to the front.
The Action Express driver subsequently grew his advantage out to around 10 seconds before being pegged back by a safety car intervention with 20 minutes left.
At the restart Albuquerque was able to contain a hard-charging Dalziel, whose car had been started by Scott Sharp and had also opted against new rubber, to secure the victory for Cadillac.
Montoya's team-mate Cameron came through to finish fifth, after being passed by Jordan Taylor (#10 WTR Cadillac DPi) and Oliver Jarvis (#77 Mazda DPi) in the closing stages.
Behind Cameron was Ricky Taylor, driving the sister Acura Team Penske effort that had been started by Helio Castroneves.
Felipe Nasr and Eric Curran were seventh in the sister Action Express Cadillac, ahead of the #99 JDC-Miller Motorsports ORECA 07-Gibson, which was the highest placed of the global-spec LMP2 runners.
Nasr had been hot on Montoya's heels during the opening stanza, but in a similar fashion to the Acura, the AXR Cadillac had its edge on the field overturned by a full service at its final stop.
Saturday's result means Albuquerque and Barbosa are the new championship leaders heading to round four at Mid-Ohio next month, having displaced Nasr and Curran at the top of the standings.
Results: IMSA Sportscar Championship – Long Beach
In GT Le Mans, Corvette's Tommy Milner benefited from late problems for the leading Porsche entry to claim victory.
Milner moved into the lead with just over 20 minutes remaining when Earl Bamber was forced to pit with right-front suspension damage to his 911 RSR.
The Corvette driver, who took over from Oliver Gavin at the stops, eked out the gap to the second-placed Ford GT of Ryan Briscoe to win by two seconds.
It was Milner and Gavin's first IMSA success since the Long Beach event last year.
Fourth in GTLM was the second Ganassi-run Ford driven by Dirk Mueller and pole-sitter Joey Hand, which finished four seconds adrift of the winning car.
Hand lost his advantage early on to Bamber's team-mate Laurens Vanthoor, but kept in sight of the Porsche through the pit stops and until the final stages before the 911's charge derailed.
Fifth were John Edwards and Jesse Krohn in their RLL-run BMW M6, while Nick Tandy and Kevin Estre finished sixth in the best-placed Porsche.