Narain Karthikeyan set the pace in Auto GP free practice on his maiden visit to Mugello.
The former grand prix driver's lap of 1m34.651s was 0.285s faster than a chasing pack led by Super Nova team-mate Vittorio Ghirelli.
After two hours of intensive testing this afternoon, Karthikeyan remained in the pits for the opening half hour of the 45 minute free practice session.
The Indian demonstrated that he required little time to warm up though by becoming the first driver to lap in the 1m34s during the session on his first flying lap.
After immediately moving into P1, Karthikeyan posted an improvement of two-tenths of a second on his second effort, setting what proved to be the afternoon's benchmark time.
Ghirelli, fastest in both of Friday's one hour tests, later joined Karthikeyan under the 1m35s barrier.
The Italian, who is driving with a fresh engine after reaching the allotted mileage on his previous unit at the preceding round in Silverstone, could not equal his fastest time from the final Friday afternoon test.
Virtuosi UK's Andrea Roda ended the afternoon in third, while Kevin Giovesi made it three Italians in the top four for Ghinzani Motorsport.
Giovesi, who lost a shock victory on his debut at Silverstone owing to making an illegal last lap pitstop, edged out Ghinzani team-mate Robert Visoiu by 0.086s.
Championship leader Kimiya Sato, who will test for Sauber in next week's Formula 1 young driver test, briefly moved into the top-six in the session's closing stages, but was demoted to seventh in the final minute by GP2 racer Daniel de Jong.
Sato's nearest championship challenger Sergio Campana, who is driving with 10 stitches in one of his legs after a farming accident, took ninth.
Manor MP Motorsport has been reduced to two cars for Dutch pairing de Jong and Meindert van Buuren this weekend, after the exit of Italian Formula 3 champion Riccardo Agostini.
2012 Formula 2 champion, and Marrakech Auto GP winner, Luciano Bacheta is another driver whose Auto GP future looks uncertain. Bacheta is absent from the Zele Racing team this weekend.
Christian Klien meanwhile reacquainted himself with a single-seater for the first time in three years this afternoon.
The former HRT, Red Bull and Jaguar driver finished 10th fastest in the opening free practice session.