Andrea Stella is calling on the FIA to clarify whether Max Verstappen's new engine in Brazil is part of Red Bull's cost cap allocation.

Following Saturday's qualifying disaster, which saw the Dutchman qualify 16th for the following day's race, his team opted to make changes to the set-up of his car.

However, it also took on a complete new power unit together with MGU-K and MGU-H, which took him over the permitted allowance (4) and thus meant he had to start from the pitlane.

At McLaren, Stella, claims that the change of engine was purely about performance, not a technical failure or even a reliability issue, and therefore wants the FIA to clarify whether such (improved performance) changes need to be included in the budget cap.

Up to now the teams have agreed to the unwritten rule that should a new engine be required due to reliability it should not impact a team's budget cap. However, improved performance is another matter entirely Stella believes, as teams could use new engines willy nilly without fear of exceeding the budget and thereby breaking the rules.

"To be honest, these kind of power unit changes, they challenge the regulations," said the Italian. "I will be interested in understanding if the cost of this engine now goes in the cost cap or not.

"If the engine was changed for performance reasons, it should go in the cost cap," he added. "So, let's see if this is the case, not that I will be able to see, as it's all on the Red Bull side. But this is also one reason why we wouldn't do it, because it would end up in the cost cap."

Red Bull boss, Laurent Mekie was quite open in admitting that the engine change was about performance.

"It's always good to fit a new engine," he said. "It's fair to say that in the last part of the season, we were on schedule to finish the year without needing the change," he admitted. "We just felt that we would take the opportunity mainly because we wanted to change the car again.

"It's difficult to give you a number," he replied, when asked the benefit of a new unit in terms of lap time, "but the gaps are small enough for everything to be important."

Stella admits however, that unlike 'the old days', a new engine does not now offer anything like the same performance gain they used to.

"I don't know how this works for Honda," said the Italian, an ironic comment when you think back to the early days of the hybrid formula, "but in general these engines don't exhibit much degradation with mileage. So that's why in general you wouldn't change an engine and accept a penalty, or a loss of positions, because normally the performance you get back doesn't really compensate for the positional losses.

"But, like I say, I'm not sure how the power degradation works for Honda."

Heading into the Sao Paulo weekend only Hamilton, Tsunoda, Antonelli, Alonso, Gasly, Colapinto, Bearman, Hadjar and Lawson had exceeded their allowance, and in each case by just one unit, which is still mighty impressive.