The Australian was first in the car when running began on Thursday in what proved to be a difficult day for the Woking squad.
Issues with the wheel brows on the MCL60 cost it time, limiting Piastri to just 52 laps, while the team amassed the lowest mileage of the 10 teams in action at just over 497km.
“We had Oscar doing most of the heavy lifting in the morning, getting the car dialled in – nothing alarming, just usual testing bugs, if you like.
“We're still understanding the car and have a lot more testing ahead of us, relatively speaking.”
New car ‘a small step' forward
Even with limited running, and accepting the fact the car is not where the team would have liked it to be, Piastri believes the MCL60 has taken a step in the right direction.
“A lot of it was about making sure the car works properly, make sure I'm getting comfy in the car and ticking all those boxes,” Piastri said of his Thursday running.
“In terms of feeling and performance, I would say it's a small step from last year.
“We know we've got a few things in the pipeline for, hopefully, soon in the season, but so far it's similar to what I remember from my limited experience in a ground-effect car.”
The young Australian had a number of outings prior to pre-season testing, both at the wheel of last year's car and previous models, resulting in making a positive impression on his new team.
“Oscar is settling in very well,” Brown said.
“Very impressed with how he carries himself, how he is in the racecar, so excited to continue testing.”
Having been in the car on Thursday morning, Piastri was back behind the wheel of the MCL60 on Friday afternoon, completing….
One further day of testing remains, with the Melburnian scheduled to take part in Saturday morning's session.
It will be his last time in the car prior to next weekend's Bahrain Grand Prix and his maiden F1 race appearance.