(Reuters) - Ferrari's Sebastian Vettel was fastest for the second day in a row in Formula One testing in Spain on Monday but champions Mercedes again did the most laps despite a water leak on Lewis Hamilton's car.
Quadruple world champion Vettel, who moved from Red Bull at the end of last year, did 89 laps before rain swept in at the Jerez circuit and was almost a second faster than the rest.
Reigning champion Hamilton did 91 laps on his first day in the new Mercedes, ending the day fourth fastest and adding to the whopping tally of 157 laps put in by his German team mate Nico Rosberg on Sunday.
"The priority right now is to put in the laps, not set fast times, and there were lots of positives today," said Hamilton. "We got good mileage and hopefully we'll get even more in the next two days."
Brazilian Felipe Nasr was second fastest in a Ferrari-powered Sauber, with Finland's Valtteri Bottas third in a Williams.
Lotus made their first appearance of the season, after arriving late and failing to get on track on Sunday, with Venezuelan Pastor Maldonado completing 41 laps in the new Mercedes-powered car.
McLaren had another tough day getting to grips with their new Honda-powered car.
After Fernando Alonso completed only six laps on Sunday. Britain's Jenson Button managed just seven on his first day at the wheel.
The 2009 champion's best and completely unrepresentative lap was more than 30 seconds slower than Vettel's fastest.
Red Bull suffered a setback when Russian Daniil Kvyat damaged the car's front wing, leaving the team without a replacement. Kvyat continued without the wing for several laps.
"As with everybody else the pressure to get the car ready on time for this test meant that we didn't have a replacement here," said race engineering head Guillaume Rocquelin.
"However, there are plenty of routine checks that need to be done, systems checks that go on all the time in the background, so we could at least get through a lot of that work today, which is why we sent Dany out for some laps without recording a time."
Red Bull said a replacement wing would arrive in time for Tuesday.
Only eight teams are taking part in the test, with Force India absent. The season starts in Australia on March 15.