F1's governing body rejected a complaint from Red Bull about the way title rival Mercedes' Formula 1 engine operates.

We reported last month that the latest technical needle between the title-warring teams was Red Bull and Ferrari's suspicions about how Mercedes managed to improve its engine this year amid the homologation rules.

"According to them, the secret is in the intercooler," Auto Motor und Sport correspondent Michael Schmidt revealed, adding that it is about the temperature of the compressed air for a 20 horsepower gain.

"The question is how far the air can be cooled and whether the sensor is mounted in a place where relevant values can be determined," he added.

But according to a Red Bull source, the complaint was "thrown out".

As a result, Red Bull's Dr Helmut Marko says the Honda-powered team is now clearly inferior to Mercedes on the straights.

"The longer they are, the more we lose. From the beginning to the end," he said.

Nonetheless, former F1 driver Ralf Schumacher thinks Max Verstappen will actually have the engine advantage over Lewis Hamilton this weekend in Turkey.

"With his new engine, I expect Max to win the race," he told Sky Deutschland, referring to the way the Dutchman scythed through the Sochi field after grid penalties to finish second behind Hamilton.

"But I expect Lewis Hamilton to hit back in the United States, providing he doesn't change his engine there," Schumacher added.

However, the German insists he has "no preference" as to who he would rather see as 2021 champion, even if he sees Verstappen as the ultimate favourite.

"That's not partisan," said Schumacher. "Both drivers are truly phenomenal and they really bring something unique.

"I have made my prediction and I am curious as to what the outcome will be."