McLaren was left frustrated by both weather conditions and a reliability issue on the final day of testing at Jerez.
The team said that blustery winds had hampered its work, and that Jenson Button had not been happy with the car, which spent the final hours parked in the garage after running into a reliability issue.
"A frustrating day of running, with windy conditions compromising our data gathering program and affecting efforts to find a satisfactory setup for the MP4-26," said a McLaren statement. "Jenson was unable to find a suitable balance with the car, and the team's progress was brought to an early end in the middle of the afternoon following the failure of an internal component."
Button still managed to complete 70 laps, but was only ninth-fastest, 1.2 seconds down on his Friday time.