"We have shown that the car is not slow. We've completed some very good work on it and we've now completed lots of laps," the German said.
"You can say we are better prepared than last year, even though we used the old car for the first race," the Autosport website quoted him as saying.
Ferrari said Schumacher lapped the Italian circuit named after team founder Enzo Ferrari and son Dino in one minute 19.664 seconds.
The German, chasing an unprecedented seventh world title and fifth in a row in the season starting in Australia on March 7, completed 98 laps in the new F2004 car.
McLaren's David Coulthard was second fastest in 1:20.950 with Colombian Juan Pablo Montoya third on the timesheets for Williams in 1:21.045.
"You can overestimate lap times like this," said Schumacher, who won last year's San Marino Grand Prix at Imola. "This is the fourth test for the car and the first showdown with the other teams."
"I don't think this (the new car) will be a disadvantage. We are confident and I'm absolutely looking forward to Melbourne."
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Schumacher was outpaced on Tuesday at Imola by younger brother Ralf in a Williams but that session was hit by rain and occasional snow.
Despite that, Ralf had few illusions about how competitive his older sibling would be.
"Ferrari will still be the team to beat," he told reporters on Tuesday.
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