Nico Rosberg topped the timesheets on the first official day of testing at a rainy Jerez circuit in Spain.
The Mercedes Grand Prix driver set a best time of one minutes 20.927 seconds during a window of dry running early in the day.
Rosberg’s time never looked like coming under threat after the rain arrived an hour into the session and the German ended the day 0.104secs up on Sebastien Buemi’s Toro Rosso.
The 24-year-old struggled to get to grips with the car in the first pre-season test of 2010 in Valencia last week, and was much more satisfied with his efforts on what was the first of eight days of testing at the Spanish circuit over the next 11 days.
“The car felt very good today,” said Rosberg, who completed 57 laps in what was the first wet-weather outing for the new MGP W01 car.
“Compared to Valencia where I was sitting too low which affected my visibility and the set-up wasn’t perfect, today I felt really comfortable and I could push so it was an enjoyable day and a good start to the test for me.
“The rain is a little frustrating but the car feels good to drive and that’s what’s important.”
Rosberg will hand over driving duties to team-mate Michael Schumacher tomorrow.
Buemi’s second-placed effort was perhaps a touch flattering given many of the cars behind him failed to set a decent time in dry window at the start of the day.
Nico Hulkenberg claimed third place – and the unofficial endurance award – after completing 118 laps on his way to a best time of 1:22.243.
Ferrari new boy Fernando Alonso took fourth at the end of 88 laps while Sauber’s Kamui Kobayashi had to be content with fifth after being limited to just 55 laps.
Jenson Button finished in sixth after a busy day which saw the reigning world champion work on the car’s aerodynamic package in the morning before the team switched focus to engine and gearbox mapping and brake materials after the rain came.
The 2010 Force India car turned a wheel for the first time in anger following its launch yesterday with Vitantonio Liuzzitaking seventh after 71 laps.
Vitaly Petrovwas eighth for Renault after just 23 laps, while the Red Bull RB6, unveiled for the first time in the Jerez pit lane this morning, was ninth in the hands of Mark Webber, the team a victim of the weather and an oil leak which forced a late engine change.
Bringing up the rear was Timo Glock in the Virgin Racing car, which has been built without the use of a wind tunnel and was making its first public appearance.
Glock completed just five laps after failing to get out on the track this morning, his best time over 17 seconds off Rosberg’s benchmark time.