Lewis Hamilton dominates Italian GP practice with new engine

Mercedes drivers Lewis Hamilton and Nico Rosberg were in a league of their own in first practice at the Italian Grand Prix.

Using an upgraded engine to spectacular effect, Hamilton was 1.588 seconds faster than the rest of the field - headed by Ferrari's Sebastian Vettel.

Carlos Sainz Jr spins off during Practice 1

The world champion was 0.463secs ahead of team-mate Rosberg, who he heads by 28 points in the championship.

Force India's Nico Hulkenberg was fourth, 1.942secs slower than Hamilton.

The German returned to the pits before the end of the session after reporting over the radio that he could feel what he thought was fuel around his backside in the cockpit. Force India are investigating.

Hulkenberg headed team-mate Sergio Perez, Williams's Valtteri Bottas and Kimi Raikkonen's Ferrari.

Vettel had a spin at the first chicane, and Toro Rosso's Carlos Sainz went off at the Parabolica, bringing the session to a brief halt for his car to be recovered.

Mercedes flexing their muscles

On Thursday, Hamilton had said that Mercedes' engine upgrade was mainly for "reliability" reasons.

Nico Hulkenberg showed an acute sense for diagnosing problems

But it later emerged that they had used in one go all their permitted remaining engine development tokens for the season.

Manufacturers were allowed 32 tokens - ascribed to various parts of the engine based on their relevance to performance - from 2014 to 2015 and Mercedes had nine remaining for use in-season after development over the winter.

The team said: "The new engine specification is effectively 2016 development pulled forward in order to make strategic use of the opportunity to use engine tokens in-season - and therefore to open up more opportunities this winter.

"Those tokens give us a development platform that allows us to run and learn about a new fuel - and with a new oil to come hopefully at a future race."

The team cautioned against reading too much into the speed-trap figures, or the lap times in Friday practice, emphasising that Mercedes were running fresh engines and the other teams "are probably on older ones".

But the upgrade appeared initially to have made a significant difference to performance.

Rosberg has admitted that he needs to start clawing back some of Hamilton's advantage but the world champion made his usual flying start to the weekend.

Uncertainty over tyres

The start of the weekend has been overshadowed by controversy over the Pirelli tyres, following two high-speed blow-outs at the previous race in Belgium.

Following an investigation into the failures, Pirelli initially insisted the teams run the tyres with a minimum pressure five psi - more than 20% higher - than the previous level of 18psi, on precautionary grounds.

Nico Rosberg is back at work after the birth of his first child

But the teams and drivers questioned the decision, with Hamilton calling it a "disaster" and Fernando Alonso saying it was "strange".

Pirelli then initially revised the instruction to 3psi higher at the rear and 4psi at the front on Thursday afternoon, and then shortly before practice reduced it again to 1.5psi higher at the rear and 3psi higher at the front.

There has been no official explanation for the changes from Pirelli as yet.

Practice results

Italian Grand Prix coverage