Loïc Duval, Allan McNish and Tom Kristensen stretched their lead at the top of the FIA World Endurance Championship points table after fending off Toyota’s challenge at the Circuit of the Americas 6 Hours in Austin on Sunday to score Audi’s 100^th sports car race victory.

Toyota’s TS030 Hybrid threatened to upstage Audi’s R18 e-tron quattro by running longer between stops and double-stinting its Michelin tyres, but the strategy fell short when it counted in the final third of the race.

Reigning world champions Marcel Fässler, Andre Lotterer and Benoit Treluyer lost ground in their title defence after a troubled race in their R18. Fässler had a disastrous opening stint. Early on he was passed by the lone Toyota of Sébastien Buemi around the outside of Turn 2, after losing momentum in a challenge on Duval for the lead. He retaliated on lap 12 only to be nudged off the circuit by the Toyota.

Fässler recovered and passed Buemi, only to launch his Audi over the controversial orange kerb stones placed on the inside of the esses to stop corner cutting. The car withstood the impact remarkably well, but the resulting damage – increased by a smack in the rear by a GT Porsche – forced a stop for repairs.

“When I hit the pyramid kerb I was not sure if I would land in Austin…” said the Swiss driver. “It was a scary experience for me. I’ve never seen sky in a sports car before.”

The champions were playing catch-up for the rest of the afternoon. Lotterer was forced to pit during his stint when he found himself stuck in fifth gear, thanks to a fuse dropping out, most likely caused by Fässler’s kerb launch. They clawed back time thereafter, but still finished a lap down on their team-mates, in third place behind Buemi, Stephane Sarrazin and Anthony Davidson.

Duval set a searing pace from the start in the number 2 Audi, but the Toyota’s tyre advantage forced the Frenchman, McNish and Kristensen to battle back past the Toyota each time they returned to the track after a stop. It was only in the final hour that the Audi crew could be sure it would thwart the Toyota challenge.

“Double stinting their tyres meant they were taking 25sec less per stint,” said McNish. “We had to wait until the end, when the circuit had more grip, before we could do the same thing. At my final stop just for fuel I knew I needed 22sec and I pulled out 34, so at that stage I knew we had it in hand.”

“We knew we would be better on degradation and double-stinting was the only chance we had,” said a disappointed Buemi, who admitted the Toyota didn’t have the pace to take on the Audis in a straight fight.

The game was up even before Buemi pitted for a splash of fuel, when he elected to hand over to Sarrazin despite the driver change lengthening the stop. “If they had changed tyres [at their final pitstop] we might have had a chance and I would have stayed in the car,” he explained. “But because they didn’t there was no point and we settled for second place.”

The Rebellion Racing Lola of Nick Heidfeld, Nicolas Prost and Mathias Beche had an uneventful run to fourth place overall, as the only privateer LMP1 entry in the race.

In fifth place overall was the LMP2-winning G-Drive Oreca-Nissan of Roman Rusinov, Mike Conway and John Martin, which was left with a comfortable lead once the pair of Oak Racing Morgan-Nissans tripped over each other in a clumsy and unnecessary collision.

Bruno Senna and Fred Makowiecki claimed GTE Pro honours for Aston Martin after setting the pace and showing strong fuel economy throughout. They beat the AF Corse Ferraris, Gianmaria Bruni and Giancarlo Fisichella finishing ahead of Kamui Kobayashi and Toni Vilander.

Bruni and Fisichella now head the GTE points standings following a disastrous non-score for the Aston Martin Vantage of Darren Turner and Stefan Mücke. The pair were joined by Corvette ALMS racer Oliver Gavin for a novel one-time-only appearance, to allow the injured Mücke to minimise his driving duties in Austin. The car was running fourth in class when Turner hit the unforgiving orange pyramid kerb in the esses. The team repaired the suspension damage and hoped to return to the track to salvage vital points, only for the stewards to block its path on the grounds that they believed the car was unsafe. The officials refused to accept Aston’s insistent argument to the contrary.

Jamie Campbell-Walter and Stuart Hall delivered the British marque a second class win after overcoming team-mates Christoffer Nygard, Nicki Thiim and Kristian Poulsen in GTE Am. Campell-Walter picked his moment carefully in the final hour to pass Poulsen at Turn 14 to secure the victory.

Fuji will be the scene of the next chapter of the WEC on October 20, with Duval, McNish and Kristensen holding a healthy 33-point lead over their team-mates in the standings with three rounds left to run. The world title appears to be within their grasp.