Jenson Button has claimed that McLaren completing more than 100 laps in pre-season testing at Barcelona "felt like 1,000".
The Woking-based constructor has struggled with reliability over the winter, but the 2009 world champion was able to rack up 101 laps in the 2015 car on Friday.
However, Button has admitted that McLaren still have plenty to do before the start of the season.
He is quoted by GPUpdate.net as saying: "It was really nice to do 101 laps. The reliability has been great today, a really big step forward and a big effort by everyone. It is amazing what you get done with a reliable car. All the tests, comparisons and aero work that you can't do because the car stops we were able to do today.
"Looking at the timing screens, we are nowhere near quick enough, but there was a lot of progress made today and a lot we can improve on over the next couple of days.
"For most teams 100 laps isn't anything, but for us it was like 1,000 laps as there is still so much for us to learn about this package."
The 2015 gets underway with the Australian Grand Prix on March 15.
