Ducati rider Andrea Dovizioso set the pace in the opening practice session of the Argentina MotoGP weekend, ousting Honda's Marc Marquez from the top spot on his very final lap.
On a dirty Termas de Rio Hondo track, times rapidly improved over the course of the session as the riders laid their rubber down, albeit times remained around four seconds off lap record pace by the finish.
Marc VDS Honda rider Jack Miler took advantage of this to spend a significant amount of time atop the timesheets, the Australian becoming the first man to dip below the 1m45s mark.
Miller had worked his way down to a 1m42.244s before Marquez went quickest on a 1m43.778s, with Dovizioso shortly slotting into second on a 1m44.194s.
It looked as if that time would be enough for Marquez to remain on top, but Dovizioso managed to go even quicker on his very last flying lap to take the top spot with a best effort of 1m43.684s.
Marquez was relegated to second, ahead of Aspar Ducati rider Yonny Hernandez, another man to set his best time after the chequered flag had fallen - the Colombian recording a 1m44.027s.
That demoted the Suzukis of Maverick Vinales and Aleix Espargaro to fourth and fifth, ahead of Valentino Rossi on the best of the factory Yamahas in sixth - the Italian also saving his best lap for last to go within half a second of Dovizioso.
Dani Pedrosa on the second factory Honda was seventh, ahead of Miller, Bradley Smith (Tech 3 Yamaha) and Scott Redding (Pramac Ducati).
Reigning champion Jorge Lorenzo had a quiet session on the second works Yamaha, finishing just over a second off the pace in 12th, five places ahead of the only faller in an otherwise incident-free session: Pol Espargaro, who crashed at Turn 7 late on.
Danilo Petrucci's replacement at Pramac Ducati, Michele Pirro, did not set a time.
|1||Andrea Dovizioso||Ducati Team||1:43.684||14|
|2||Marc Marquez||Repsol Honda Team||1:43.778||+0.094||16|
|3||Yonny Hernandez||Aspar Racing Team||1:44.027||+0.343||16|
|4||Maverick Vinales||Team Suzuki ECSTAR||1:44.113||+0.429||17|
|5||Aleix Espargaro||Team Suzuki ECSTAR||1:44.128||+0.444||16|
|6||Valentino Rossi||Yamaha Factory Racing||1:44.181||+0.497||13|
|7||Dani Pedrosa||Repsol Honda Team||1:44.231||+0.547||14|
|8||Jack Miller||Estrella Galicia 0,0 Marc VDS||1:44.244||+0.560||20|
|9||Bradley Smith||Tech 3||1:44.275||+0.591||16|
|10||Scott Redding||Octo Pramac Yakhnich||1:44.293||+0.609||19|
|11||Hector Barbera||Avintia Racing||1:44.455||+0.771||17|
|12||Jorge Lorenzo||Yamaha Factory Racing||1:44.742||+1.058||13|
|13||Loris Baz||Avintia Racing||1:45.080||+1.396||18|
|14||Eugene Laverty||Aspar Racing Team||1:45.294||+1.610||15|
|15||Alvaro Bautista||Aprilia Racing Team Gresini||1:45.447||+1.763||17|
|16||Stefan Bradl||Aprilia Racing Team Gresini||1:45.519||+1.835||18|
|17||Pol Espargaro||Tech 3||1:45.590||+1.906||18|
|18||Andrea Iannone||Ducati Team||1:45.792||+2.108||17|
|19||Tito Rabat||Estrella Galicia 0,0 Marc VDS||1:45.876||+2.192||22|
|20||Cal Crutchlow||Team LCR||1:46.086||+2.402||11|