Why is Antonelli taking grid penalties on home soil in Italy?

Kimi Antonelli could lose ground in the championship this weekend as he will start from the back in Sunday's Italian Grand Prix; watch every session of the Italian GP live on Sky Sports, starting with Friday's practice sessions at 11.30am and 3pm

Championship leader Kimi Antonelli is highly unlikely to be in contention for victory on home soil at this weekend's Italian Grand Prix.

Antonelli will start at the back of the grid as he will exceed the limit of four power units that can be used in a season before incurring grid penalties.

It means the Mercedes driver could see his 59-point lead over team-mate George Russell and Ferrari's Lewis Hamilton cut significantly, while a third consecutive win for McLaren's Lando Norris could enable the reigning world champion to make major inroads into his 83-point deficit to Antonelli.

With Mercedes having confirmed that Antonelli is taking a grid penalty for changing his engine at this weekend's Italian Grand Prix, Sky Sports F1 explain why the world championship leader has opted to do so at his home race.

Mercedes have generally had the car to beat for most of this year, particularly earlier in the season, but the W17 has suffered from reliability issues.

In Antonelli's case, he suffered an electrical shutdown when running in second at the Barcelona-Catalunya Grand Prix in June, which damaged one engine.

Then Mercedes discovered an issue with his engine after July's British Grand Prix, which led the team to fit Antonelli with a fourth engine at the Belgian Grand Prix three races ago, meaning he was already on the limit of the number of power units that can be used before suffering from grid penalties.

F1 power units are split into different components. Had Mercedes only changed the internal combustion engine, which would be Antonelli's fifth of the season, the Italian would only have a 10-grid place penalty.

But Mercedes boss Toto Wolff says Antonelli will "take the full thing", meaning they will change other components that will take him above their respective limits, including the energy store and control electronics. They will both be worth five-grid places each, thus taking Antonelli to 20 grid places.

Once a driver has a 15-grid place penalty or more, the FIA automatically puts you at "the back of the grid", which will happen to Antonelli in Monza.

Monza is known for its long straights, so overtaking is relatively easy compared to other upcoming tracks such as Madrid and Baku, which are street circuits.

At the 2021 Italian Grand Prix, Valtteri Bottas powered through from the back to the podium after an engine change, while Max Verstappen won from 14th at the 2022 Belgian Grand Prix.

"Monza is an energy-starved circuit with four overtaking zones. A driver cannot defend all of them, so a faster car should be able to make progress relatively straightforwardly," said Mercedes trackside engineering director Andrew Shovlin on the team's Nu Silver Arrows Radio Show .