Audi took the race win and manufacturers' title in the Intercontinental GT Challenge deciding California 8 Hours, but third was enough to give Mercedes' Tristan Vautier the drivers' championship.
Christopher Mies, Christopher Haase and Kelvin van der Linde drove the Land Audi R8 to outright victory at Laguna Seca.
Van der Linde had led away from pole, with WRT Audi driver Robin Frijns trying to put Raffaele Marciello's Strakka Mercedes under pressure for second and Vautier stuck behind Stuart Leonard in fifth.
By the time Vautier found a way around Leonard, he was 20 seconds off the lead after half an hour of racing and made no noticeable progress in the first stint.
Marciello moved into the lead just before the first hour ended, then handed over to Maxi Gotz during a subsequent full course yellow.
The Land Audi then had to serve a drivethrough penalty for passing under yellow and fell to 12th.
Mies recovered to sixth by the time the car received a second drivethrough, this time for an unsafe release from the pits.
By now somewhat off-strategy, following the next round of stops, Mies stayed out and went back into second behind another off-strategy car - the #8 Bentley of Andy Soucek.
Bentley then benefited from subsequent yellows fitting its strategy, and it led into the final three hours.
But Lewis Williamson in the Strakka Mercedes took advantage of Maxime Soulet in the leading Bentley getting caught up in traffic, and dived down the inside into the Andretti hairpin.
Williamson was ordered to give back the place having run off track to complete the pass, and by then also had to keep an eye on Vautier appearing in his mirrors.
Williamson retook the lead as Soulet ducked into the pits to hand over to Soucek, and the Strakka car pulled away from Vautier in traffic.
Following the Mercedes and Audi stops, Soucek was back into second but with 2h35m to go the Bentley got trapped by GT4 traffic.
Winkelhock and Mies zoomed around the outside exiting the Corkscrew and through the Rainey Curve, while Soucek clipped a GT4 BMW M4 and sent it into the sandtrap.
The Bentley incurred a left-rear puncture, couldn't turn into the pitlane and so had to complete a slow lap on three tyres and one wheel rim. It also had to serve a drivethrough for the collision.
The leading Strakka team then pitted one lap later than its rivals in a full course yellow caused by the GT4 GMG Audi and fell to seventh by the time Marciello rejoined.
Those stops left Haase leading Frijns and Alex Riberas in an Audi 1-2-3 with Maxi Buhk in Vautier's SunEnergy1 Mercedes in fourth ahead of Vincent Abril's Bentley and Dirk Werner's 911.
Marciello stormed into fourth place, past the car Buhk shares with Marciello's title rival Vautier, yet almost immediately tried an impossible manoeuvre around the outside of Riberas' Audi at Turn 5, and fell off the track and back down to fifth - two spots behind Buhk.
Dust and dirt in the air duct hurt the Strakka car's power output thereafter and he gradually fell to six seconds behind Riberas and 20s off Buhk.
The Audis made their final schedule stops as soon as they could - with 65mins of drivetime left - and Marciello did likewise, to clear dust off his windscreen, inside and out.
Van der Linde and Dries Vanthoor took over the two lead Audis in the final stint, with Maro Engel third in Vautier's car.
Marciello made quick progress from sixth to fourth, but by that time he was 24s behind his title rival's Mercedes and had to make two further pitstops to have debris cleared.
That left him seventh at the flag as third for Vautier's car gave the sometime IndyCar driver the title and Audi's one-two sealed its crown.