Kamui Kobayashi is confident that the Sauber team has a solid base from which to work with the new Ferrari-engined C30 after setting the sixth fastest time on the first day of testing in Valencia.
The Japanese, who is heading into his second season, refused to draw any conclusions about the potential of the car after lapping 1.852 seconds off pace-setter Sebastian Vettel.
But despite a difficult day during which the team battled sensor problems, he was content with progress.
"The car is okay," said Kobayashi when asked by AUTOSPORT for his impressions of the car. "At the moment, I can't really judge it and we had a lot of things to test. But the car is okay.
"We had a lot of sensor programmes so didn't get through all of the programme possible. We did test work with the car, but it was basically just to check everything was working. That was our day. We still have to get a set-up, but we haven't had time."
Kobayashi added that the degradation of the new Pirelli rubber had improved since he first tried them in last November's Abu Dhabi test, but that the tyres were still consistent.
"I was quite surprised as they have changed the tyres since Abu Dhabi," he said. "They improved the degradation but it's very difficult to work on the car with the tyres not being consistent. "But it's the same for everybody and they have tried to improve the tyres on long distance work."