Two-time defending Formula One world champion Sebastian Vettel posted the fastest time in testing at the Montmelo circuit in Spain on Tuesday.
The 24-year-old Red Bull driver clocked a fastest lap time of 1m23.265 in his 79-lap spell on the circuit.
“One thing is for sure, the cars have less grip than last year (due to new rules),” said Vettel. “But I felt good and it was a good day. We took a long break at lunch in order to make adjustments, but nothing was broken.”
His compatriot, Nico Hulkenberg, put in the second fastest time in his Force India car.
“It was a very positive day and the car was very balanced,” said the former Williams driver, who failed to get a drive last year.
Lotus, though, did not have a great day, despite having recorded the quickest times out of all the 2012 cars at a previous testing session in Jerez.
French driver Romain Grosjean had such a serious problem with his car's chassis that the team have decided to pull out of testing for the rest of the week.
“It wasn't an easy decision to take but it would be more productive to do this, working on both chassis,” said team director Eric Boullier.
“Our design department has already found a solution and we will be back for the final session of testing.”
Testing continues here until Friday and there will be a final series of testing back here on March 1-4, before the teams travel to Australia for the opening race of the season in Melbourne on March 18.
TEST TIMES - 21 FEBRUARY
1. Sebastian Vettel (Red Bull-Renault) - 1m23.265
2. Nico Hulkenberg (Force India-Mercedes) - 1:23.440
3. Lewis Hamilton (McLaren-Mercedes) - 1:23.590
4. Daniel Ricciardo (Toro Rosso-Ferrari) - 1:23.618
5. Fernando Alonso (Ferrari) - 1:24.100
6. Michael Schumacher (Mercedes-AMG) - 1:24.150
7. Sergio Perez (Sauber-Ferrari) - 1:24.219
8. Bruno Senna (Williams-Renault) - 1:25.711
9. Heikko Kovalainen (Caterham-Renault) - 1:26.035
10. Romain Grosjean (Lotus-Renault) - 1:26.809
11. Charles Pic (Marussia-Cosworth) - 1:28.026