The Brazilian-American driver, who raced for Fortec during the past season, was sampling the Charouz-run Lotus team's car.
Fittipaldi set the fastest time in morning session, a 1m27.416s, before lowering his benchmark to a 1m27.392s in the afternoon to retain his position at the top of the classification.
"It's been a really good day of testing," said Fittipaldi, who finished 10th in the 2016 standings.
"It has been very nice to work with the whole Lotus team, they did a great job and I'm really happy.
"It took us a couple of runs to get the pace [in the morning] and once we got it we put the new tyres on and produced the quickest time."
Monday pacesetter Damiano Fioravanti continued his impressive adaption to the category by taking second spot in the morning for his regular EuroFormula Open team RP Motorsport.
Fortec runner Dorian Boccolacci set the pace in the early laps, before Fioravanti came to the fore as temperatures rose.
The session was red-flagged on six occasions after problems for Rene Binder, former Auto GP and GP3 racer Facu Regalia, 2016 FV8 3.5 race winner Matevos Isaakyan, Alfonso Celis Jr, the Mexican's AVF team-mate Henrique Chaves and Steijn Schothorst.
After the final interruption, only Binder and Yu Kanamaru improved their times, with the Japanese securing the third best morning time, just 0.062 behind Fioravanti.
GP3 man Schothorst ended Tuesday with the second fastest time of the day thanks to a 1m27.701 set in the afternoon.
Kanamaru repeated his morning position of third, repaying a late night from the Arden team to prepare his car.
The afternoon session featured fewer red flags, although former Formula Renault 2.0 Eurocup title challenger and GP3 racer Kevin Jorg hit trouble in his Teo Motorsport machine.
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