Sebastian Vettel maintained his position at the top of the timesheets on the second day of F1 testing in Jerez, while both Mercedes and McLaren-Honda were forced to end their days early due to technical issues.

On his second day in the SF15-T, Vettel led the way for almost the entirety of the eight-hour session, improving his benchmark to 1min 20.984secs in the afternoon before light rain an hour from the chequered flag spelled the end to any further changes in the classification.

A full 1.6secs quicker than he managed on his first day in the car and completing 78 laps, Vettel was also a clear eight-tenths faster than second place driver Felipe Nasr, who made it a Ferrari-powered 1-2 in the Sauber C34.

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The Brazilian set his best time shortly after Vettel, en route to completing 75 laps, while Williams' Valtteri Bottas ended the day as the best-placed Mercedes-powered driver in third position.

Meanwhile, having managed 157 trouble-free laps in the hands of Nico Rosberg on Sunday, Mercedes ran into problems with Lewis Hamilton at the wheel on day two. Diagnosed as a minor water leak, Mercedes had hoped to get the Englishman back on track before the end of the day, but ongoing issues and the onset of rain scuppered those intentions.

Despite this, it was still a very productive day for the defending champion, Hamilton completing 91 laps - still more than any other driver - bringing Mercedes' tally up to 246 laps in just two days.

By contrast, McLaren's dismal start to the 2015 season showed no signs of abating as Jenson Button spent much of his day in the garage, mechanics poring over the Honda-powered MP4-30. Despite claims that the team is on top of the car's mechanical issues, Button managed just six very slow laps over the course of the day, bringing its total up to just 12 over 16 hours of track time.

Also suffering problems was Red Bull, albeit only after Daniil Kvyat suffered a 'small' off early on and damaged the only RB11 front wing currently in Spain. Forcing the team to focus on minor development work, Kvyat was sent out to complete slow laps with no wing attached at all, which was a big set-back for both the Russian and the team.

Elsewhere, Lotus made its belated debut with the Mercedes-powered E23 Hybrid, Pastor Maldonado completing 41 laps before a problem ended his day early, while Max Verstappen got laps in the dry and wet as he continues to get acquainted to the rigours of F1 and the Toro Rosso.