Kimi Raikkonen says he is quite happy with Ferrari's Kinetic Energy Recovery System after his first tests in the new Ferrari F60 at Mugello.
Ferrari said last week that they are unsure whether to use KERS from the start of 2009, having previously admitted that they were behind schedule with the device.
But Raikkonen, who drove the F60 for the first two days of this week, said he felt the system was functioning well.
"Both days the use of KERS had positive results," he told Gazzetta dello Sport. "The system works well like every other new component."
The former world champion isn't sure that it will have a huge effect on the racing, though.
"You have more power but for such a short time that I think it won't change things much," said Raikkonen. "Maybe it's an interesting invention, but I don't think it's decisive."
Ferrari decided to test at Mugello rather than joining their main rivals at Portimao because they expected better weather in Italy, but in the event both locations have been hit by rain this week.
However Raikkonen stood by the team's decision.
"I think it's raining over there too," he said. "At least here we're close to home and it's easier to send people back and forth when needed."