The 39-year-old, now an occasional test driver for his former team, was third fastest in one minute 22.428 seconds on the first day of Formula One's final pre-season test in Barcelona on Monday.
It was the first time the German had driven the F2008 after participating in several tests for the Italian team last season. Ferrari are using his expertise because electronic driver aids have been removed for this season, which starts on March 16.
"This Ferrari can fight to win right from the first race," Schumacher was quoted as saying in Tuesday's Gazzetta dello Sport.
"But you have to pay attention because without the electronic aids everything depends on you. It is all in your hands and in your head."
Briton Lewis Hamilton was fastest on Monday in a McLaren and Ferrari's Finnish world champion Kimi Raikkonen second.
Schumacher dismissed speculation he would race in this season's Italian MotoGP race at Mugello after getting on two wheels during tests with Ducati last year.
"It is an absolute lie. At the most, I can race on a scooter," he said.
(Writing by Mark Meadows, editing by Rex Gowar)
