Brendon Hartley set the fastest lap so far of the Lone Star Le Mans meeting at Austin to head a Porsche one-two in third practice.
The Kiwi's best lap was a rapid 1m46.435s in the No.17 Porsche 919 Hybrid that he shares with teammates Mark Webber and Timo Bernhard, 0.346s quicker than Neel Jani’s sister No.18 machine.
Porsche appears to have a clear single lap pace advantage over the chasing Audi R18 e-tron quattros, which appear to be more competitive in slightly cooler evening conditions.
The best of the Audis was 1.001s behind the leading Porsche, Loic Duval setting a best of 1m47.436s in the No.8 R18 e-tron quattro.
The No.7 Audi continued to claw back mileage after losing most of the first practice session on Thursday due to an alternator failure. The Andre Lotterer, Benoit Treluyer and Marcel Fassler crewed No.7 car finished the 60-minute session fourth on a 1m48.207s.
Toyota continued to place in their now-customary fifth and sixth positions. The No.2 TS 040 HYBRID led the No.1 car, Mike Conway and Sebastien Buemi setting the best times for the two Japanese machines respectively.
Signatech leads the way in P2
The LMP2 class featured a surprise pacesetter in the form of Signatech's Alpine A450B, with Paul-Loup Chatin setting a 1m56.178s lap. This time was still 0.3s off Sam Bird’s best from second practice.
Second was the Hong Kong-entered KCMG ORECA 05, Nicolas Lapierre setting a 1m56.655s as the team chase a third successive WEC class victory.
Oli Webb took the Team SARD Morand Morgan Evo to the third best time. The British racer turned in a 1.56.454s to place third ahead of the No.30 Extreme Speed Motorsport Ligier-HPD driven by Ryan Dalziel.
The title chasing No.26 G-Drive Racing Ligier-Nissan was only seventh in class after an incident with the Dempsey Proton Racing Porsche 911 RSR at Turn 10. Both cars returned to the track after a red flag was waved for parts of the Ligier being deposited on the racing line.
Porsche was again quickest in the LMGTE Pro category, with the No.92 Porsche 911 RSR driven by Patrick Pilet at the head of the timing screens with a 2m05.134s lap, two tenths clear of the #51 Gianmaria Bruni/Toni Vilander Ferrari 458.
In LMGTE Am, the No.98 Aston Martin of Pedro Lamy headed the class with a best lap of 2m06.639s.
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