Neel Jani posted the quickest time for Porsche during the opening session of the FIA World Endurance Championship Prologue test.
The defending world champion turned in a best time of 1:32.068s towards the end of a dry four-hour morning run at the 3.6 mile Autodromo Nazionale Monza.
Jani's time was approximately half a second slower than the pole figure for the 2008 1000km of Monza, which was the last race held at the circuit featuring LMP1 machinery.
Jani is sharing the #1 Porsche 919 Hybrid with new team-mates Andre Lotterer and Nick Tandy.
Second quickest on Saturday morning and just 0.158 seconds off the pace was the Toyota TS050 driven by Anthony Davidson.
WEC Prologue Saturday morning times
The gap between Davidson and Jani was closer than any of the margins between Porsche and Toyota at last year's Prologue, held at Paul Ricard.
Toyota's sister car finished third on a 1:37.491s effort, with the second Porsche sandwiching the Japanese manufacturer's two cars.
Only the Nissan-powered ByKolles CLM P1/01 failed to set a lap time during the opening session of the two day public test.
In GTE-Pro, Porsche's new 911 RSR topped the class timesheets courtesy of a 1:47.379s run by Michael Christensen.
Only the pair of Ford GTs and the second Porsche kept to within a second of Estre's remit, with the Ferrari 488s and Aston Martin Vantages struggling to match the pace of their rivals.
Andy Priaulx recorded the second-quickest time in class, two tenths shy of the pace.
Rebellion Racing took a one-two in the LMP2 times led by a time of 1:36.094s from Bruno Senna, while Gulf Racing set the pace in GTE-Am.
Saturday's second run takes place during the afternoon, between 14:00 and 17:00 local time. A night session is scheduled for later in the day.
