Jenson Button ended the day sixth fastest in the Honda-powered MP4-31, but with an impressive 84 laps under his belt - more than he and team mate Fernando Alonso managed over the first four days of testing last season.
“We’re in a much better position than last year, which is great,” Button said afterward. “Everything ran smoothly, no reliability issues, so not too bad.
“It’s too early to say if we’re quick or not. Today is more about having an understanding - there are lots of different things we have on the car which are all big improvements on last year.”
Button highlighted the energy recovery systems (ERS) as a specific area where the team have improved, adding: “Deployment, for the races, is somewhere we will be able to make up a lot of time - I'm very happy with the progress that has been made in that area. Other areas need more work, but that area is a definite improvement.”
Racing director Eric Boullier echoed Button’s thoughts, saying the day had helped rebuild confidence within the team.
“We are definitely better,” he commented. “All the numbers were correlating with what we expected. That means our tools are working properly - and that means we know the car is better than last year.
“I won’t say how much better [than last year’s car], because that might build the wrong expectations - and we also don’t know what others have done. But the car is correlating, which is good.
“There have been good improvements [on Honda’s side], I think. Clearly they are on the right path, and clearly they have fixed a few issues with hurt us last year, so it’s good - so far.
“To be honest you never get to being 100 percent happy, so we always have to improve - and every time you get closer to the limit you find things to improve. But we are definitely okay.”
Alonso will get his first run in the MP4-31 on Tuesday at the Circuit de Barcelona-Catalunya, where testing continues until Thursday.