Felipe Nasr has stated that the Sauber C35 is "a step forward in everything" compared to its 2015 predecessor, after getting the new car's first laps in on Tuesday in Barcelona.
Sauber was forced to run the 2015-spec car during the first week of testing at Catalunya, but its new challenger finally took to the track - and completed 103 laps - on the first day of week two.
"It was impressive to have clocked that amount of laps in our first day," said Nasr, having ended up ninth out of 12 on the timing screens.
"Normally I would expect more things to need fixing, but it was quite a smooth day overall. Still a lot of work to be done though, I'm sure we're gonna see a progression of the car over the next days.
"But the first impression was quite good, it felt like a step forward from last year from the chassis, from the engine, gearbox side - it just felt like we have a step forward in everything."
He added: "Back-to-back with the car from last week, it just felt like we have a more stable rear - when looking at medium or high speed corners."
Better engine driveability
While the other cars carrying Ferrari's 2016-spec engine suffered mechanical issues on Tuesday, Sauber's run was largely trouble-free - and Nasr praised the new version of the power unit.
"The engine has impressed me with the driveability being better: the whole response of the engine, the speed range being more progressive and more consistent," he said.
"The feeling is a lot better, you can anticipate things going into the corner. And this has also helped calm down the rear of the car."
But points might be tough
However, Nasr had to concede that the other midfield teams also appear to have made progress from 2015 - and that challenging for points in Melbourne could be difficult.
"From my point of view, it looks like teams are a lot more competitive this year than they were at the beginning of last season, you know.
"The field seems to be a lot tighter now - so to be in that position of scoring points, at the moment it does sound difficult. But I'm not judging anything yet."
Additional reporting by Jonathan Noble