Despite being impressed with Red Bull's latest F1 offering, world champion Sebastian Vettel says that it is too early to start speculating about the season ahead.

With three days of testing in the books, Red Bull's RB9 has looked ready to follow in the wheel tracks of its title-winning predecessors, but Vettel is wise enough to point out that trying to compare the various teams and cars given that there is every chance that they are following different programmes that prevent direct comparison.

The German only took over from team-mate Mark Webber after the Australian handled the initial shakedown and development of the car, but completed 102 laps of his own on Thursday, reporting that the RB9 was already streets ahead of where the RB8 had been at a similar stage of its development.

"The last time we were here was exactly one year ago and the car back then was miles behind what we have now," he confirmed to journalists at Jerez, "The good news is that everything worked super and is reliable. There haven't been any issues and, speed-wise, it looks pretty solid. It definitely is a step forward from last year."

Despite his enthusiasm, however, Vettel expected almost every driver to feel the same way at some point over the four days.

"It's been said a hundred times and I'll say it again: there hasn't been much of a regulation change, so I would say that most cars pick up from where they left off in 2012," he reasoned, "Visually, the car hasn't changed much - the real changes are underneath and, there, it is paramount that everything works, so the two days that Mark did - and my running - are good news.

"I felt good in the car, but it is definitely too early to make any predictions. Is the car a winner? You only know that at the end, so I'll be damned if I would give a verdict!"

Vettel ended his first day third on the timesheets, but reported that RBR had not been chasing quick laps, and was unconcerned about the pace set by Ferrari's Felipe Massa.

"Not at all," he insisted, "We haven't been looking for speed today - we left the speed rush to the others. My guess is that some were running on low fuel. Our programme is what really matters and for me to get into the groove again. And guess what? It worked without any major hiccups."