Jerez F1 test: Kimi Raikkonen fastest for Ferrari on final day

The 2007 world champion spent most of the day at the top of the times, running on the medium and hard-compound tyres during the morning, before switching to some soft-tyre running late in the afternoon.

Raikkonen reiterated his belief that Ferrari has started 2015 in encouraging shape.

"Compared with the last car it feels at lot better," he said.

"We still have a lot of things to work on and things to improve, but we have something we can work on and the team has done a good job over the winter to prepare and make this car.

"We can be happy about that, but it's still early days."

It was during a sequence of runs on the yellow-sidewalled Pirellis that Raikkonen set the best time of the four days, going one tenth of a second faster than Ferrari team-mate Sebastian Vettel managed on day two (on mediums).

Sauber once again got itself towards the front as it completed some soft-tyre running for the fourth consecutive day, with Marcus Ericsson edging out Lewis Hamilton's Mercedes for the second-fastest time with half an hour to go.

Ericsson caused a last-minute red flag when his car ran out of fuel on track.

Hamilton succeeded in passing the 100-lap mark for the first time at this test, after a water leak limited him to 91 on day two.

The reigning world champion did not have a perfect day though, as a spin at the chicane brought out the red flags in the morning.

It was only a minor delay to Mercedes' programme, with Hamilton returning to the track just 40 minutes after he caused the stoppage.

At the other end of the timesheets, Lotus and McLaren both wrapped up the test early due to power unit and fuel pump problems respectively, while Red Bull lost time with an ERS problem earlier in the day that forced Daniil Kvyat to stop on track in the morning.

McLaren had a troubled morning as well, when an "operational issue relating to the oil level" caused a delay to its programme in the morning.

Button finished the day with 35 laps to his name, and he set the Honda-powered MP4-30's fastest lap of the week with a 1m27.660s.

WEDNESDAY'S TEST TIMES: