Rosberg has Mercedes smiling

Nico Rosberg finally put a smile on the face of everyone at Mercedes as he piled on the laps at Jerez on Thursday.

Rosberg was halted by an electrical fault on the opening day of pre-season testing on Tuesday while team-mate Lewis Hamilton crashed out 24 hours later following brake failure.

The pressure was on the team to emerge unscathed on Thursday and they were relieved to report a clean bill of health after Rosberg completed 148 laps - the equivalent of two grands prix distances.

"We were just massively unlucky the last two days with problems that could have been easily avoided, but they've also been so difficult to fix, which is also very unusual," said Rosberg.

"But today we showed we have a very reliable car. We really made up for it. Nothing at all went wrong, not the slightest thing, which is good.

"It really put a smile on everybody's face. To drive from Silverstone to Spa, distance-wise, in a test day with an F1 car with no problems whatsoever, pounding out the laps, being very consistent, is a fantastic achievement.

"So I'm very excited about today because it was a great test day as we were consistent and we got through everything we had on the plan."

Hamilton, who returns to the car on Friday to conclude the first of three tests before the season kicks off in Australia on March 17, will be hoping for a repeat of Rosberg's reliability.

"I'm sure it's going to be the same," Rosberg added. "That will really kickstart our programme."

The 27-year-old finished second on Thursday with a best lap of one minute 18.766 seconds, sandwiched between the pacesetting Ferrari of Felipe Massa and reigning three-time world champion Sebastian Vettel, making his first outing in the new Red Bull.

Jenson Button, who was quickest for McLaren on Tuesday, was down in seventh but only because he concentrated on aero and mechanical work.

The Briton's day ended five minutes early after he stopped the MP4-28 on track, apparently due to a loose wheel following a pit stop.

Massa, meanwhile, was happy to finish top of the standings with the fastest lap of the week so far - a 1:17.879.

His fastest lap came on the quicker soft tyre, and the Brazilian is refusing to get carried away.

"It was an important three days for us to find the right direction to work on the car, even if I didn't do as many laps as I expected to do," said Massa.

"We've improved the car and my lap was a good one, but ahead of the championship, 100 per cent I have my feet on the ground."

Vettel was equally circumspect about his car's potential after clocking up 102 laps, with his best a 1:19.052.

Asked if he could fight for victory from the opening race, Vettel said: "It's too early to tell. I think it will be very, very close.

"It might be there is a certain favourite after these tests, but it could be completely the opposite in Australia.

"So I expect it to be at least as tight as last year. The regulations haven't really changed, so it's difficult to make up a lot of ground.

"Equally, if you are in the front, it's difficult to find something extra."

On his first outing in the new Lotus, Kimi Raikkonen set the fourth quickest time, but only completed 40 laps.

Force India gave James Rossiter another run this morning, the Briton finishing sixth, within a tenth of a second of Raikkonen and Toro Rosso's Jean-Eric Vergne in fifth.

Paul di Resta, who churned out 184 laps over the first two days, took over from Rossiter in the afternoon but an exhaust failure restricted him to just seven laps.

On his second day for Marussia, Max Chilton proved he is getting up to speed as he went ninth quickest with a lap of 1:21.269.