Kevin Magnussen has downplayed the pace that saw him finish half a second ahead of the chasing pack on Day Three at Jerez.
Making his McLaren debut in the new MP4-27, the Danish rookie completed 52 laps with a best time of 1:23.276.
That time put him 0.424s up on second place Felipe Massa and 1.7s ahead of his McLaren team-mate Jenson Button, who finished fourth quickest after running in the morning.
"It felt good," Magnussen said. "Pretty pleased with the reliability so far and pleased to get so many laps done in half a day. So pretty positive.
"As we all know it's winter testing and no one really knows what the other cars or teams were doing, so not looking into that too much.
"It wasn't a 'balls to the wall' lap but we were pushing. We are trying to get good data and I'm trying to learn about the car.
"Everyone is pushing but you have so many different things that can play a part in what lap times you are doing, so not looking into that."
He added: "I didn't really set any expectations. I was hoping to get a lot of laps and I was hoping to learn. So we had a positive day in that respect. We got some good laps and I learnt a lot, so I'm happy."
As for the fact that Thursday's running was his debut, 21-year-old admits he had a few nerves the night before.
"I had butterflies in my stomach, I struggled to sleep - I'm excited. I'm a rookie.
"I'm sure everyone was. It's new cars, new season. It's a massive opportunity for me. This day was big for me as a first test as a race driver."