The Finn's lap of one minute 17.221 seconds around Barcelona's Circuit de Catalunya was the second fastest of the eight days of winter testing and slower only than team mate Sebastian Vettel's best on Thursday.
McLaren's Fernando Alonso had a rollercoaster day, sidelined for nearly five hours by an oil leak and engine change before charging back out to set the second quickest time on the same hypersoft tyres.
The Spaniard, who completed 93 laps after failing to set a time in the morning, was 0.563 slower than Raikkonen.
Compatriot Carlos Sainz was third fastest for Renault, after losing time to a gearbox problem in the morning.
Australian Daniel Ricciardo was fourth in a Red Bull and Frenchman Romain Grosjean completed an impressive few days for Haas in fifth.
"I think we will be close enough to be in the hunt," said Ricciardo, who now heads to a season-opening home race on March 25. "It's been a better winter than last year.
"Ferrari turned it up the last couple of days but we are there or thereabouts. It looks like Ferrari can challenge Mercedes if we can't and it could be quite close."
Grosjean did a marathon 181 laps in the Ferrari-powered car on Friday, more than anyone else on a day that started cool but warmed up, while compatriot Esteban Ocon put in 163 for Force India.
Four times world champion Lewis Hamilton shared the Mercedes with Finnish team mate Valtteri Bottas, the pair doing 97 and 104 laps respectively as they focussed on long runs rather than outright speed.
(Reporting by Alan Baldwin, editing by Ken Ferris)
Share
