Lewis Hamilton pips Nico Rosberg in Italian GP practice
Lewis Hamilton pipped team-mate Nico Rosberg to the fastest time in second practice at the Italian Grand Prix as Mercedes left their rivals trailing.
The world champion beat Rosberg by just 0.021 seconds, with Ferrari's Sebastian Vettel third fastest but 0.759secs off the pace.
Sergio Perez performed well during second practice finishing fourth
The day's running suggested an upgraded engine had moved Mercedes even further clear of the field.
The design used up all of the team's permitted in-season engine development.
The new engine is available only to the factory team. Mercedes were not able to give a date for when customer teams Lotus, Force India and Williams would receive it.
Nevertheless, the Mercedes-powered Force India cars of Sergio Perez and Nico Hulkenberg were fourth and fifth quickest, ahead of Ferrari's Kimi Raikkonen and the Lotus of Romain Grosjean.
The Frenchman's team-mate Pastor Maldonado was eighth fastest, ahead of the Mercedes-engined Williams of Valtteri Bottas and Felipe Massa.
Lewis Hamilton arrived for practice at Monza on his motorbike
Hamilton would take his seventh victory of the 2015 season if he wins at Monza on Sunday (live at 13:00 BST on the BBC Sport website and 5 live, highlights on BBC One at 17:05).
The Briton leads the drivers' world championship by 28 points from team-mate Rosberg.
Echoes of the last race
The list of fastest times suggested a similar competitive picture to the last race in Belgium, where Grosjean took the final podium place and Perez finished fifth.
The events of Spa continued to echo in other ways, too, with tyres a major topic of conversation following the high-speed blowouts suffered by Vettel and Rosberg over the weekend in Belgium.
Pirelli has imposed stricter tyre usage limits this weekend following the problems, and on Friday the Mercedes drivers, Vettel and Fernando Alonso were called to a meeting also involving F1 boss Bernie Ecclestone, Pirelli and leading team bosses.
All four had expressed concerns or criticisms of Pirelli following the Spa failures.
Pirelli insists two changes to the recommendations on tyre usage issued in the space of one day on Thursday were due to extra data and research rather than the criticisms from the drivers.
Problems for McLaren and Red Bull
It will be a difficult weekend for McLaren and Red Bull, both teams using this high-speed track to introduce tactical engine upgrades because they expect to be uncompetitive as a result of the power deficit of their Honda and Renault engines.
Jenson Button had a disappointing session, managing only three laps
All four of their drivers will be hit with grid penalties as a result of using more than their permitted number of engines.
On top of that, McLaren driver Jenson Button managed only three laps because of reliability problems, and the team went as far as to test on Alonso's car a cooling package aimed at the next race in Singapore, which McLaren expect to be their most competitive race for the remainder of the season.
Red Bull's Daniel Ricciardo and Daniil Kvyat were 13th and 22nd fastest and Alonso and Button 16th and 21st.