For the second time in three days of testing, Audi Sport's Romain Dumas set the fastest lap of the day ahead of Saturday's 14th annual Petit Le Mans powered by Mazda. The Frenchman set a lap of 1:09.550 (131.474mph) in Wednesday's two-hour session at Road Atlanta in the Audi R18 that he will share with Timo Bernhard and Marcel Faessler.

A total of 55 cars posted times in the final day of testing prior to official practices for the 2011 finale of the American Le Mans Series presented by Tequila Patrón. The top four diesel-powered cars – two Audis and two of Peugeot Team Total's Peugeot 908s – were within 0.484sec around the 2.54-mile circuit.

"The car is still quite good," Dumas said. "We tried a couple of different settings but it is tough to get feedback. It is very difficult to make a judgment with so many cars on the track. The race will be extremely challenging. The traffic will make you take a lot more risks now than in previous years."

Peugeot's Franck Montagny was second quickest at 1:09.641 (131.302mph) in the Peugeot 908 that he will share with Stephane Sarrazin and Alexander Wurz. The second Audi of Dindo Capello, Tom Kristensen and Allan McNish was third at 1:09.875 (130.862mph); Kristensen set the time.

Jaime Melo was the quickest GTE Pro driver for Risi Competizione and Ferrari. Melo – driving Risi's Ferrari F458 Italia with Raphael Matos and Toni Vilander – posted a time of 1:20.102 (114.154mph) for a scant 0.029-second gap back to Corvette Racing's Oliver Gavin. Close margins were the theme throughout the class; the top nine cars were within 0.839sec.

The Corvette C6.R, also driven by Richard Westbrook and Jan Magnussen, set a best lap of 1:20.131 (114.113mph). Next up was AF Corse's Ferrari of Gianmaria Bruni, Giancarlo Fisichella and Pierre Kaffer at 1:20.269 (113.917mph).

Signatech Nissan's Jean-Karl Vernay set the fastest LMP2 time at 1:13.852 (123.815mph) in the Nissan-powered ORECA 03 that he will drive with Franck Mailleux and Lucas Ordonez. The young Frenchman was 0.190sec quicker than Level 5 Motorsports' Christophe Bouchut in his HPD ARX-01g; he is sharing the car with Joao Barbosa and Scott Tucker. The second Level 5 HPD of Luis Diaz, Marino Franchitti and Tucker was third in P2 at 1:14.719 (122.379mph).

Gunnar Jeannette led a 1-2 showing for CORE autosport in LMP Challenge with a lap of 1:17.298 (118.295mph) in the ORECA FLM09. Jeannette, teaming with Ricardo Gonzalez and Rudy Junco, was just 0.297sec quicker than Ryan Dalziel in the sister CORE entry. Dalziel will drive with Jon Bennett and Frankie Montecalvo.

Intersport Racing's Kyle Marcelli was third fastest in LMPC with a lap of 1:18.126 (117.042mph). He will drive with Tomy Drissi, Chapman Ducote and David Ducote.

In GTE Am, Rui Aguas went quickest for AF Corse in the Ferrari F430 GT he will drive with Justin Bell and Rob Kauffman at 1:21.196 (112.616mph). He was 0.872sec ahead of another Ferrari – the Krohn Racing entry of Nic Jonsson, Tracy Krohn and Michele Rugalo. Larbre Competition's Corvette C6.R of Patrick Bornhauser, Julien Canal and Gabriele Gardal was third at 1:23.550 (109.443mph).

Black Swan Racing's Jeroen Bleekemolen set the pace in GT Challenge with a lap of 1:25.772 (106.608mph) in the Porsche 911 GT3 Cup that he will drive with Sebastiaan Bleekemolen and Tim Pappas. Leh Keen was second in class for Alex Job Racing at 1:26.339 (105.908mph); he will team with Bill Sweedler and Brian Wong. TRG's Dion von Moltke was third quickest at 1:26.392 (105.843mph). He will drive with Ben Keating and Jim Norman.

Thursday's first practice session is set for 10 a.m. ET.