Bottas fastest again as Raikkonen crashes

New signing Valtteri Bottas put champions Mercedes on top of the timesheets with the fastest lap so far in Formula One's pre-season testing, while Kimi Raikkonen crashed his Ferrari.

Bottas's best lap of 1 minute 19.310 seconds came on supersoft tyres in the morning session on Wednesday, with the Finn then handing over to triple champion team mate Lewis Hamilton (79 laps) for the afternoon.

Kimi Raikkonen's day didn't end well. (AAP)

The time was 0.395 faster than the best set last week, also by Bottas on ultrasoft tyres, and quicker than any Spanish Grand Prix pole position time since the Circuit de Catalunya layout was changed in 2007.

It was also nearly three seconds faster than Hamilton's 2016 pole time.

Bottas, who did 70 laps on Wednesday, joined from Williams in January as replacement for retired world champion Nico Rosberg.

The Finn's former teammate Felipe Massa, who was fastest on Tuesday when he did an eye-catching 168 laps equal to two-and-a-half race distances, was second quickest and completed another 63 laps.

Raikkonen was third with a time of 1:20.406 but spent some time in the garage while Ferrari carried out a fluid systems check and he completed just 39 laps before lunch.

The Finn crashed into the barriers at turn three in the afternoon.

McLaren's Fernando Alonso was 3.7 seconds off the pace and managed only 46 timed laps with the team still struggling with their latest Honda engines.