Sebastian Vettel described his impression of the new Red Bull-Renault RB5 as 'positive' after his first full day of testing in the car at Jerez yesterday.
Vettel, who managed only 14 laps in Monday's shakedown before stopping with a gearbox problem, completed 61 laps on Tuesday.
He was fastest of the four 2009-specification cars running, ending up second on the timesheets behind Sebastien Buemi's 2008 Scuderia Toro Rosso, despite missing the last half-hour after a problem with a gearbox sensor forced him to stop on track.
"The first impression is positive," he said when asked by autosport.com what he thought of the car. "We made big progress, we did a lot of laps taking into consideration that the car just finished its build on Monday morning.
"Unfortunately we had to stop before the end of the session, but so far the feeling is good in the car."
Despite being impressed by the RB5, Vettel believes it is too early to make any performance comparisons with his rivals.
"It's the first day, so let's keep our feet on the ground," he said. "It's difficult to say where we will be. The other teams are starting to find their way, but for us it's a long way.
"It was important to have some laps and collect some data, but after one day it's way too early to judge."