Brendon Hartley says his return to the WEC with Porsche in China last week was a 'tricky' affair after his 'mindblowing' F1 debut.
It's been a pressure-packed few weeks for Hartley who continues to dovetail his WEC commitments with his new F1 opportunity.
After his baptism of fire with Toro Rosso in Austin and Mexico, the 27-year-old Kimi was off to Shanghai for the penultimate round of the World Endurance Championship with Porsche.
Hartley secured the WEC's drivers' crown in China along with his Porsche team mates Timo Bernhard and Earl Bamber.
But his return to his most familiar racing environment still required a bit of adaptation.
"It was actually surprisingly tricky to get back in the car," Hartley recalled.
"I thought I would feel right at home, [it's] been home for the last few years. Took a few laps to feel comfortable again - having a roof over your head, the seat position is different."
As he compared the two very distinct experiences, Hartley revealed why his first F1 laps were a complete "shock to the system".
"I guess, Austin, the big shock was high speed, just in terms of driving," he said.
"They are amazing, these cars, especially in the first sector. It was mind-blowing, so it took some getting used to.
"You always want more grip and more power, but it was a bit of a shock to the system.
"No other real surprises, I knew it was going to be a challenge, I knew the level of driver/teams was the highest you can find - I guess there were no big surprises and I kind of expected that."
Hartley believes the complexities of driving a modern LMP1 charger provided him with a solid foundation for F1.
"From working with Porsche the last years, it made my transition quite smooth," Hartley said.
"It is a similar number of people involved, the structure, the pressure - driving at Le Mans with Porsche is a big amount of pressure.
"All those things I have learned to deal with, but there are a lot of other things to learn. I am aware there are still a lot of things to learn."