World champion Marc Marquez dominated practice for the Argentina MotoGP at the brand new Termas de Rio Hondo track on Friday.
The Spanish Honda rider is seeking to make it three wins out of three this season as the world championship returns to Argentina for the first time since 1999.
And the 21-year-old proved a quick learner as he made light of the alien surroundings to top the times by over one second from his teammate Dani Pedrosa.
"It was a fun day, it is always interesting to learn all the different corners and their secrets at a new track and the practice sessions go by more quickly," said Marquez after clocking 1min 39.313sec.
"I am happy with how this first day went and with the base that we have. We shall continue working in the same way, as we are aware that tomorrow's times will be much closer."
In third came the Yamaha of Aleix Espargaro, Stefan Bradl (Honda) took fourth with Ducati's Andrea Dovizioso completing the top five.
Former double world champion Jorge Lorenzo had posted the quickest time in first practice but the Yamaha rider plummeted down to ninth overall after the second session.
His first session time of 1min 42.804sec was almost five seconds slower than the one Marquez was to set later.
Yamaha's nine-time world champion Valentino Rossi, who raced in the 250cc division when Argentina last hosted a world championship event 15 years ago, was eighth fastest with 1min 41.395sec.
"A difficult day in Argentina at the new track. The conditions are not fantastic and we are struggling very much with the tyres, especially the rear," said Rossi.
"In the afternoon it became a bit better and we worked well with the bike but we still haven't found the right balance so we have to work to make it better.
"We have to concentrate on making the tyre work harder as after a few laps the rear slides a lot. We hope the conditions of the track improve but we will also work to improve the setting of the bike for tomorrow."
Marquez is on a three-timer after winning the season-opener in Qatar one month after breaking his leg, doubling up in the Grand Prix of the Americas.
The youngest ever world champion leads the MotoGP standings by 36 points from Pedrosa going in to Sunday's race.
Australia's Jack Miller emerged quickest in Moto3 practice.