Despite a problematic day, which saw the German complete just 37 laps, Sebastian Vettel topped the timesheets at Barcelona as the penultimate pre-season test got underway.

A damp start to the day gave the teams a chance to test the intermediate Pirelli tyres, before conditions began to dry mid-morning.

Vettel had a couple of minor offs during the morning session, and as a result the Austrian team opted to complete some precautionary checks over lunch.

"Unfortunately, we didn't complete many laps today, as we had a long break," said Vettel, "longer than expected. It wasn't anything big, nothing broke, but at the test if you think there might be a problem then you'd rather take the car apart and check. The boys did their best and we still got some runs towards the end of the day - not as much as we'd like, but the car feels good and hopefully we'll do more tomorrow."

"It was frustrating today, as we lost some time making checks to the car during lunch," added head of race engineering, Ian Morgan. "It's what testing is for, but we would have liked to complete more laps today."

For much of the day it was Fernando Alonso who headed the timesheets as Ferrari continues to show strong pace and reliability. The F150 is still in the same configuration seen at Valencia as the Maranello outfit continued to focus on understanding the Pirelli tyres and working on the overall reliability of the car.

The day went smoothly with no technical problems and by the end, a total of 101 laps had been completed. "Overall, it was a positive day," the Spaniard told the team's website. "We did a lot of laps and brought home much valuable information. It seems that, on this track too, there is a certain level of tyre degradation, but it is only the first day and we have to see how the track evolves between now and Monday."

Toro Rosso made good use of the damp start to proceedings, Jaime Alguersuari putting in a 20 lap run on Pirelli's intermediate tyre, thereby gathering useful data for team and the new tyre supplier.

Once the track had dried, the slicks came out and two runs were completed before the lunch-break - which is compulsory at this track. The afternoon's work included a brake system evaluation.

Sauber - which had Kamui Kobayashi on duty - lost track time due to a powertrain problem, but was still able to gather data. The Japanese driver completed 78 laps on his way to posting the fourth best time of the day.

"We couldn't complete the whole programme due to a technical problem," said Kobayashi. "We had wet conditions in the morning so this was fine to collect some information on wet tyres. In the afternoon we couldn't do everything we planned, so we have some work left for tomorrow."

"It was a wet start this morning, so we decided to do a wet tyre programme," explained technical director, James Key. "Pirelli brought the wet race spec tyre here and, as we had already tried the intermediate race spec, we decided to use the opportunity to get to know the wet tyres. This was useful because the track started to dry up by mid-morning, and we were able to learn how both, the wet and the intermediate tyres behave on a drying track, which is always useful.