Max Verstappen gave a provisional thumbs-up to Red Bull's 2018 challenger after his first day behind the wheel of the RB14.
"It was a positive day, so I am pretty satisfied," he reported after completing 67 laps at the Circuit de Barcelona-Catalunya.
"It is still early and you always want to fine-tune the balance," he said. "But the first impression is very positive, more so than last year."
Verstappen's best time of 1:20.326s was good enough for fourth place on the days' timesheets. However, he said it was too early to compare the car's performance against those of his rivals.
"I don’t know if the car is good for victories. I only drove this car once and I think nobody has shown anything yet.
"However, I do know when a car is performing well or not. And this car is performing well. We have no problems, and that is a big difference with last year."
His team mate Daniel Ricciardo had been in the race seat on Monday and set the fastest time on the opening day of pre-season testing. Verstappen's turn had to wait until Tuesday, and was then further delayed because of a problem with the fuel system.
"This morning we had a fuel leak," Verstappen explained. "After which we checked the whole car.
"The weather wasn’t great and since the track was still damp at that moment, we did not really lose any track time."
Verstappen said that despite the delay and the weather conditions, he had still got through the day's intended program of work.
The chilly conditions that persisted for most of the day - and ended with light sleet and snow - made a detailed evaluation of the RB14 impossible.
"It was very cold today, so it was very difficult to get the tyres working," he pointed out. "After I left the pits, I simply had to go full out to keep the temperature in the tyres - improving time one lap at a time."
The unusually freezing weather in Barcelona is forecast to persist for the rest of the week. Wednesday could even see significant snowfall, which would bring testing to a complete standstill. Not that this would directly affect Verstappen, who is handing back the car to Ricciardo for the day.
"Regarding the weather, tomorrow doesn’t look very positive," he agreed. "Thursday, I get back in the car and then we’ll make as many runs as possible."