BARCELONA, Spain (AP) Mercedes and Ferrari set the pace in the first week of preseason testing in Formula One.
Kimi Raikkonen was fastest with Ferrari on Thursday as the teams completed a four-day session outside Barcelona, while Valtteri Bottas ended with the quickest time of the week with Mercedes.
The two teams showed better pace and reliability from the start, indicating that they will likely be a step ahead when the season begins on March in Australia.
Another four-day test session at the Circuit Barcelona-Catalunya will be run next week.
After testing wet tires on an artificially soaked track, drivers were able to switch to slicks and Raikkonen topped the timesheets with a lap of 1 minute, 20.872 seconds, almost a second faster than Max Verstappen of Red Bull.
''I didn't pay attention to what the other teams were doing, nor the lap times, because at this point, it means nothing,'' Raikkonen said. ''I've got the feeling that we learned some lessons from last year and, at the moment, we can't complain about how testing has gone so far.''
Bottas, replacing retired champion Nico Rosberg, set a time of 1:19.705 seconds on Wednesday, the fastest since layout changes were made at the track. He was only eighth fastest on Thursday after Mercedes had to deal with a mechanical failure in the morning session.
The failure kept teammate Lewis Hamilton from running.
''Electrical fault kept us in the garage this morning, so I've decided with the team not to drive today as I wouldn't have learned much,'' Hamilton wrote on Twitter. ''Shame not to drive but it's been a great few days. The guys have done an awesome job. Can't wait to be back in the car next week!''
Romain Grosjean impressed with Haas, running a total of 118 laps, the most among all drivers on Thursday.
''It's been a productive day for us,'' Grosjean said. ''We managed to get some wet running, inter running, pit stop practice, dry running, and trying a few setup changes that we had thought about overnight. The car is getting better and better.''
Felipe Massa couldn't get on the track after Williams discovered chassis damage caused by Lance Stroll's crash on Wednesday, and Toro Rosso's Daniil Kvyat managed nothing more than an installation lap because of a power-unit failure.
New rules to bring more excitement to the series gave cars more grip and downforce, making them significantly bigger and faster than in previous years. Teams expect times to drop even more in next week's sessions.
Tire supplier Pirelli soaked the track's surface overnight with the help of eight water tanks, allowing teams to test this season's wider tires on the wet. The watering trucks soaked the track again after the morning session to give drivers more time on the wet-weather tires.