Sebastian Vettel edged out Esteban Gutierrez to put Red Bull on top on the final morning of pre-season testing at Jerez.
Pedro de la Rosa's first day with Ferrari came to a smoking halt just two laps in when his gearbox failed, while the morning was cut short by disintegrating kerb that could threaten the afternoon running.
It was Vettel who started the day brightest, and for much of the morning the reigning world champion - on his second day in the RB9 - was the only man to have broken the 1m19s mark.
Gutierrez was the first to join him in Sauber's C32, posting a 1m18.669s which sent him provisionally top.
Moments later though Vettel responded by shaving a further tenth of a second off the benchmark, with his 1m18.565s proving unmatched for the rest of the morning.
Lewis Hamilton enjoyed a far more promising second morning in the Mercedes W04, racking up 59 laps and going third fastest following a late run on the medium compound.
That was in stark contrast to his first official test for the team, which was cut short when a brake failure sent him into the barriers at Dry Sack.
Less than four hundredths of a second covered the 2008 world champion, his predecessor Kimi Raikkonen in the Lotus E21 and his McLaren replacement Sergio Perez in the MP4-28.
Jean-Eric Vergne was next up in Toro Rosso's STR8, with Valtteri Bottas just over one second back in Williams 2012-spec FW34.
Force India's 2012 third driver and 2013 race seat aspirant Jules Bianchi went eighth fastest on his first - and at present only - day with the team.
Charles Pic and Luiz Razia rounded out the day's runners, although de la Rosa propped up the timesheets after his early gearbox issue prevented him from completing a single flying lap.
Gutierrez had also caused a red flag when he stopped out on track on what Sauber later confirmed was an out-of-fuel run.
Morning times Pos Driver Team Time 1. Sebastian Vettel Red Bull 1m18.565s 2. Esteban Gutierrez Sauber 1m18.669s + 0.104 3. Lewis Hamilton Mercedes 1m18.905s + 0.340 4. Kimi Raikkonen Lotus 1m18.915s + 0.350 5. Sergio Perez McLaren 1m18.944s + 0.379 6. Jean-Eric Vergne Toro Rosso 1m19.331s + 0.766 7. Vlatteri Bottas Williams 1m20.426s + 1.861 8. Jules Bianchi Force India 1m20.585s + 2.020 9. Charles Pic Caterham 1m21.919s + 3.354 10. Luiz Razia Marussia 1m25.796s + 7.231