Ferrari driver Felipe Massa clocked the fastest time of Formula One's opening preseason test in his new F138 car on Thursday, giving the Italian team hope it may have overcome the lack of speed that spoiled its title chase last year.
Mercedes, meanwhile, rebounded from an incident-packed opening two days with Nico Rosberg completing a session-high 148 laps at the Jerez circuit.
Rosberg's car had spouted flames and smoke on Tuesday, and the next day new teammate Lewis Hamilton crashed his vehicle into a barrier.
"I think it was probably a personal record for me to do almost 150 laps," Rosberg said. "I've never been so well prepared physically as I am this season. I feel on top form and it was no problem to complete the program.
"To drive the distance from Silverstone to Spa in one day with no problems whatsoever is a fantastic achievement from the team. It really made up for the last two days and put a smile on everybody's face."
Hamilton will be back behind the wheel on Friday for the final day of testing in southern Spain.
New Sauber driver Esteban Gutierrez had the second-most laps with 110 and world champion Sebastian Vettel was third with 102.
Massa, who is representing Ferrari alone with Fernando Alonso not attending the tests in his home country, recorded a fastest lap of 1 minute, 17.879 seconds. Rosberg and Vettel were next.
The Brazilian's pace is a good sign for Ferrari, which saw the championship slip through Alonso's grasp down the stretch last season mainly because he just simply couldn't keep up with Vettel's Red Bull.
Ferrari's new test driver Pedro de la Rosa will take over on Friday.
Vettel was pleased with his first real drive in this year's car after teammate Mark Webber had gone out during the first two days of the test.
"It was great to get back in the car, to get rid of the rust and to get back in the groove again," Vettel said. "The first feeling is good and the car is working well. It's difficult to judge the speed, but in terms of reliability it looks pretty good. For today we accomplished what we set out to achieve, which was to put a lot of laps on the car.
The season begins with the Australian Grand Prix on March 17 after two more sets of tests in Barcelona.