By Alan Baldwin
JEREZ, Spain, Feb 7 (Reuters) - Formula One world champion Sebastian Vettel shook off the winter rust with his first test of the year on Thursday while Felipe Massa raised the hopes of Ferrari fans with the fastest lap of the week.
Mercedes also put the teething problems of the first two days behind them with 2008 champion Lewis Hamilton's German team mate Nico Rosberg completing a mammoth 148 laps - a total of 655km in one day.
Vettel, pounding out the laps in the Red Bull for the first time since he won his third consecutive title in Brazil last November, was only the third fastest but the times were of secondary importance.
"It felt good to be out there and back in the car. The car is working very well... I'm really happy with the car so far," the German told reporters crowded around the Red Bull trucks at the back of the garage.
"It's good to get back in the car as soon as possible, to get into the groove again, get used to the tyres," added the 25-year-old.
"It was important to do a lot of laps today and get back into the rhythm and get rid of the rust that was on my shoulders over the winter," he said after completing 102 laps in the Spanish sunshine.
Massa's team mate Fernando Alonso has skipped this first test, preferring to wait until the second in Barcelona on Feb. 19 for his first drive in the new F138 and leaving it to the Brazilian to put on the mileage.
Massa did that, completing more than 1,000km over the three days with a best lap of one minute 17.879 seconds on soft Pirelli tyres.
The Brazilian had said on Tuesday that Jenson Button's fastest lap of 1:18.861 in the McLaren had been 'incredible' given the conditions and hard tyres and he was clearly happy with his own.
"I didn't have the car to do this lap time on the first day and we didn't even try," he said. "I thought the lap was impressive and I'm sure many people are thinking the same about me now.
"For sure we improved the car. There were some areas where I found improvement in the grip and driving. I think it was a good lap but we have to wait and see exactly what we are going to have at the beginning of the championship.
"I have absolutely 100 percent my feet on the ground."
Rosberg was the second fastest on the third day with 2007 champion Kimi Raikkonen making his first track appearance of the year in the Lotus with the fourth best time.
"The E21 feels quite good so far, even if the balance isn't quite to my liking yet," said the Finn, whose car had a clutch problem late in the afternoon.
"That didn't stop us going through the programme we wanted to do which had a lot of aero runs in it. We know the car can go faster, we were just running through what we needed to achieve."
Finland's Valtteri Bottas made his first appearance as a fully-fledged F1 driver in last year's Williams, run with aerodynamic parts for the new season.
The first race is in Australia on March 17. (Reporting by Alan Baldwin, editing by...)