Valtteri Bottas and George Russell have to swap their Mercedes engines ahead of the US Grand Prix.

Earlier it was announced that Sebastian Vettel will get a new German power source.

It is another indication that there are reliability problems at Mercedes.

Bottas is already going to his sixth engine in Austin, while there is a limit of three per season.

The Mercedes driver will only get a new combustion engine and will receive a five-place grid penalty for it.

In George Russell's Williams - which is also powered by a Mercedes engine - more parts are replaced, so that the Englishman seems sentenced to a start at the back of the grid on Sunday.

In Vettel's Aston Martin, exactly the same parts are replaced.

Mercedes team boss Toto Wolff said during the previous Grand Prix in Turkey that there are concerns within Mercedes about reliability.

Especially the combustion engine, the V6, is under a magnifying glass.

According to Wolff, this produces 'special sounds'.

Fifth engine change at Hamilton not excluded

Lewis Hamilton, who is involved in an intense title battle with Max Verstappen, received his fourth combustion engine of the season in Istanbul.

That put him on a ten-place grid penalty.

With a possible switch to a fifth engine, the Englishman has to go five places back, something that is not excluded by Wolff.

Verstappen already paid a heavy grid penalty earlier in the season for a fourth completely new power source.

That change was necessary because the World Cup leader lost an almost new Honda engine in a serious crash during the British Grand Prix.

The Japanese manufacturer has no further concerns about reliability

United States GP times

  • Second free practice: Friday 10 p.m.

  • Third free practice: Saturday 20:00

  • Qualification: Saturday 11 PM

  • Race: Sunday 9 p.m.

Keywords: engines, valtteri bottas, mercedes, reliability problems, indication, source.it, george russell, sebastian vettel, us, grand prix, power source, grid penalty, toto wolff, german, engine change