"I was out on track and had a look at a couple of the corners," the rookie Sauber racer is quoted by Germany's Auto Motor und Sport.
"I was surprised by how different the cars are. I think Red Bull is in a very good position, which can be seen easily from the outside.
"The Red Bull and the Lotus are the most stable," he continued, according to Italy's Tuttosport.
"They will fight for the title this season.
"I was very impressed with the Lotus in the cornering," the 21-year-old continued.
"It has incredible grip, far more than the others, not moving around at all.
"The Red Bull is also very smooth, with no uncertainty in the trajectory, very well balanced and very good at the front end."
In Switzerland's Blick, veteran correspondent Roger Benoit compiled the first tentative pecking-order list for 2013, with Red Bull and Lotus in first and second places.
Third is McLaren, ahead of Ferrari, Mercedes and Sauber.
Mark Webber told reporters on Friday: "We are in a good position to be strong in Melbourne, as you would expect from a team that has had our results in the past few years."
World champion Sebastian Vettel is also happy.
"It's true that I only felt comfortable in the car in the second half of last season," he is quoted by Sport Bild.
"It's also true that the handling of the new car is very similar."
After testing the impressive black and red E21 in Spain, Raikkonen headed to Moscow for a demonstration ice race.
"I can't promise that we are going to be able to fight for wins," the Finn told R-Sport, "but I think we will be up there and we will have ourselves a chance at least."