JEREZ, Spain - Behind the wheel of his new Mercedes Formula 1 car, Lewis Hamilton felt right at home. The former McLaren driver, tested his team's 2013 new in Jerez, Spain.Hamilton said: "I'm happy. It's still got a Mercedes engine, so it has all the power I used to have."Hamilton will be driving with Nico Rosberg in 2013 and Mercedes hopes to rekindle the fiercely competitive spirit they shared as kart rivals 13 years ago.'FANTASTIC REPLACEMENT'Hamilton commented on his new team mate: "I've known him longer than any other driver here. It's a real privilege to work alongside him."Team principal Ross Brawn said: "They're good friends. Hamilton's speed is unquestioned. With Michael Schumacher coming to the end of his career, he's a fantastic replacement."First around the Jerez circuit in the new car was Rosberg, who said it felt very good and he could "straight away push hard".Rosberg said: "It's a fresh start. We're going to push each other. We need to close the gap to other teams."'DON'T WANT TO FADE'Brawn said Mercedes would use two development teams in 2013, "one on developing the 2014 car and one just for this one".The cars' performance suffered in 2012 when engineers began concentrating on developing the next ones, he said.Brawn said: "We don't want to fade in 2013, as we did in 2012. There's a lot of innovation under the skin of the car which I'm pleased about."New developments would be added quickly, beginning with a new front wing, which would be unveiled for testing on.Hamilton said he was confident Mercedes would close up on its rivals: "In 2012 they were sometimes almost two seconds off the pace, I'm hoping for a great improvement. "I've got double the buttons I used to have, I've already got rid of some of them, but there is still much to learn before I can give good feedback."