The World Endurance Championship points-leading Porsche edged out both Audis in a close opening practice session for the 6 Hours of Bahrain.
A 1:42.107s effort by Neel Jani stood as the quickest time of the LMP1 runners during the 90 minute afternoon run.
The Swiss driver has a chance to claim the WEC title during Saturday’s six hour contest with team-mates Marc Lieb and Romain Dumas.
Second fastest during opening practice was the #8 Audi R18 driven by Loic Duval, which finished 0.343 seconds down and a further 0.065 seconds ahead Benoit Treluyer in the sister Audi.
Seven tenths of a second off the pace was Kamui Kobayashi in the #6 Toyota TS060.
Kobayashi plus team-mates Mike Conway and Stephane Sarrazin are the only other drivers capable of winning the championship this weekend.
Read our 6 Hours of Bahrain preview for all the title permutations
Sixth quickest was the #1 Porsche 919 Hybrid of Mark Webber, Brendon Hartley and Timo Bernhard which finished on a 1:42.956s time ahead of the #5 Toyota.
Rebellion Racing led Bykolles Racing in the LMP1 privateer order thanks to a 1:46.366s effort from Matheo Tuscher.
The sole Rebellion R-One did experience a brief hiccup when Dominik Kraihamer spun at turn four, but the Austrian was able to continue without damage.
In LMP2, Nicolas Lapierre set the fastest lap of the session for the French Signatech Alpine squad.
The Frenchman’s 1:50.966s marker was enough to eclipse the second placed Manor ORECA of Roberto Merhi by 0.189 seconds.
Third in class was the Jota-run G-Drive Racing ORECA driven by Alex Brundle, with the RGR Sport by Morand Ligier of Filipe Albuquerque in fourth.
GTE-Pro saw both Aston Martins ascend to the top of the order, with Darren Turner taking control of the session in the #97 Vantage.
Turner’s 1:58.735s benchmark pipped the sister car of Nicki Thiim by four tenths of a second.
Both turbocharged Ford GTs struggled to match the pace of the naturally aspirated Astons following a balance of performance ruling prior to the 6 Hours of Bahrain.
The #67 Ford finished fifth in class and one second off the pace, while the #66 car book-ended the class in seventh.
Third in GTE-Pro was the Dempsey Proton Racing Porsche 911 RSR driven by Richard Lietz, which finished on a 1:59.420s time.
The turbocharged Ferrari 488s entered by AF Corse lapped fourth and sixth respectively.
In GTE-Am, Emmanuel Collard led the way in the #83 AF Corse Ferrari 458 Italia.
A brief seven-minute Full Course Yellow truncated the session after 34 minutes when Aston Martin’s Am car – driven at the time by Paul Dalla Lana – went off at turn one.
A second free practice session for the WEC 6 Hours of Bahrain is scheduled later today at 19:30 local time.
