Valtteri Bottas, who has taken grid penalties at three of the last four races, is hoping that he's done with new engine components for the remainder of the season.

At Monza, though he won Saturday's Sprint, the Finn started the Grand Prix from the back of the grid after taking on a new ICE (internal combustion engine), turbocharger, MGU-H and MGU-K.

Two weeks later, the Finn took a 10-place drop - leaving him just ahead of Max Verstappen - after taking on a new ICE, turbocharger and MGU-H in what Mercedes described a "strategic" move.

Finally, last weekend at COTA, Bottas dropped five places after taking on another new ICE.

At a time customer teams have also been taking on new components and Toto Wolff admits there is concern over the Mercedes power unit's durability, some wonder if Bottas, who leaves for Alfa Romeo at season end, is being used as a guinea pig by the German team in favour of his teammate.

Certainly, the Finn hopes there will be no further penalties over the remaining five races.

I really hope we're done for now," he said. "I think both engines that I've got in my engine pool, they seem to be OK, we haven't detected any issues with any of them.

"So, fingers crossed I can go to the end without penalties," he added, "because now, in this tight championship battle, even if you just lose five places, it really compromises the race.

"I think it has been a case of just being unlucky," he insisted, "because before bringing the engines to the track they have to pass all the tests, reliability tests. So in theory they should be OK.

"But luck hasn't been on my side," he admitted, "I've had more failures. It's just unlucky but we just hope now that everything is fixed. Time will tell."