Heikki Kovalainen sampled Caterham's CT03 for the first time and reckons it is trickier to find a balance compared to 2012's CT01.
The Finn returned to track action for the first time since last year's Brazilian Grand Prix to help Caterham pinpoint the issues with the CT03.
"The main priority today was to help give my impressions of the 2013 car in the spec it ran in for the first three races this year against the car I raced last year, and to give my feedback on the 2013 tyres," he said.
"The first impression I had was that this car, which is obviously closer to the 2012 car than what will be raced for most of the rest of the season, is certainly trickier to find a balance on than the 2012 car, and the 2013 tyres go off a lot faster than last years".
Kovalainen nevertheless warned that one 90 minute session is insufficient time with which to draw a concrete conclusion.
"After one session I clearly haven’t had enough time in the car to find out how much we could change the handling with setup alterations, but I’ve been able to give the team a lot of feedback that I think will be useful this weekend on setup and tyres, and looking ahead to Spain where we’ll have more new parts."