Romain Grosjean put the seal on an impressive test at Mugello for his Lotus team by going fastest on the final afternoon.
His best - a 1m21.035s set with two hours of the afternoon to run - was the quickest any driver managed across the three days.
The Frenchman had also topped the second day of running at the Italian circuit, Lotus having opted to alter plans and give him both days of testing following the day one washout.
Sebastian Vettel's morning best was enough to keep him second for Red Bull, less than one tenth of a second ahead of Ferrari's Fernando Alonso.
The Spaniard had set the early running in a Ferrari featuring revisions to its exhaust exits and rear bodywork, but an hour in he went off and nudged the wall at Turn 12, leading to delays of more than two hours for the Scuderia.
Toro Rosso's Daniel Ricciardo closed to within a quarter of a second of Alonso in the afternoon, ending the day fourth fastest.
Sergio Perez finished six tenths of a second down the road in fifth, having triggered one of several red flags on the final day when his Sauber stopped on the main straight at the exit of the pitlane.
Nico Hulkenberg, taking over from Paul di Resta for the final afternoon, was less than one tenth of a second slower in sixth.
Di Resta was initially tucked up behind his Force India stable-mate, but late improvements from Pastor Maldonado, Oliver Turvey and Nico Rosberg forced him down to 10th.
Rosberg (Mercedes) set new bests on his final two tours to jump into eighth, 0.082s behind Maldonado's Williams.
Turvey meanwhile completed a low-key test for McLaren, which opted not to run either of its two race drivers, by finishing ninth ahead of Heikki Kovalainen and Timo Glock.
Kovalainen was the busiest driver of the day, completing 138 laps in the Caterham.
Pos Driver Team Time
1. Romain Grosjean Lotus-Renault 1m21.035s
2. Sebastian Vettel Red Bull-Renault 1m21.267s + 0.232s
3. Fernando Alonso Ferrari 1m21.363s + 0.328s
4. Daniel Ricciardo Toro Rosso-Ferrari 1m21.604s + 0.569s
5. Sergio Perez Sauber-Ferrari 1m22.229s + 0.879s
6. Nico Hulkenberg Force India-Mercedes 1m22.325s + 0.975s
7. Pastor Maldonado Williams-Renault 1m22.497s + 1.147s
8. Nico Rosberg Mercedes 1m22.579s + 1.229s
9. Oliver Turvey McLaren-Mercedes 1m22.662s + 1.312s
10. Paul di Resta Force India-Mercedes 1m23.002s + 1.652s
11. Heikki Kovalainen Caterham-Renault 1m23.169s + 1.819s
12. Timo Glock Marussia-Cosworth 1m23.466s + 2.116s
All Timing Unofficial