F1 testing: Ferrari's Sebastian Vettel 'very positive' after first day

The German had a relatively trouble-free day, completely 69 laps with a leading time of 1m24.939s, 0.440s clear of Lewis Hamilton in the Mercedes.

"The car is a step forward," said Vettel. "It was the first proper day and it was good to get some laps and a first feel for the car.

"The first impression was very positive.

"It's better to be first in one month's time. It's better than being last but it's not really important.

"We're fairly happy with the car, the way it felt.

"Ideally, we'd like to do some more but naturally when everything is new, you have issues you look into and you take a little bit more caution.

"You stop, you have a look and these things take time."

Mercedes completed 156 laps - the equivalent of two and a half race distances in Barcelona and just over double that of Ferrari but Vettel was unconcerned.

"It looks like they had a decent day," he said. "For us, we didn't do that many laps but overall we have plenty of reason to be happy.

"The interesting bit is to see what the others are doing.

"We saw a bit of that today. The next couple of days will be quite interesting.

"We have plenty of things we need to improve and time is limited.

"It's not a secret in four weeks we will be in Australia so yeah that's why we have a lot of work to do.

"There is plenty of stuff to get on top of which is normal for a new car."

Ferrari made a huge step forward with its power unit last winter that helped it finish second in the constructors' championship in 2015.

With regards this year's spec, Vettel said: "We tried to make improvements.

"Last year, the guys did a miracle and they've been working hard so naturally it is better than it was."