McLaren enjoyed a productive start to the final pre-season test of the year in Spain, with Jenson Button second quickest on a day where the team insisted it was looking for 'quality over quantity'.
Button completed just 64 laps at the wheel of the new MP4-27, with only Pastor Maldonado completing fewer on a more troubled day for Williams.
However, the limited number of laps from the Briton was tied into McLaren's programme for the week, which includes the introduction of a range of new components onto the car ahead of the season opener in Melbourne later this month.
With pit-stop practice and set-up work forming the basis of the first day's programme, Button was able to complete the work required with team manager David Redding pleased with a productive session on track.
“Having completed more than 2000km at Barcelona last week, today was always going to be more about quality than quantity,” he said. “We wanted to drill a little deeper into our understanding of the car, and that meant undertaking some bigger set-up changes that wouldn't ordinarily be available to us during a grand prix weekend.
“We made good progress and we're satisfied with today's results.”
Button will be back in action on Saturday, with Lewis Hamilton taking to the track on Friday.