Mercedes says that there is no guarantee it will maintain its engine advantage for the remainder of the season – even though it still has development tokens left.
The German car manufacturer has been dominant so far this season, despite Ferrari denying them two wins on the back of big progress with its power unit.
Although both car makers still have seven tokens left to play with over the second half of the season, Mercedes motorsport boss Toto Wolff says there remains the possibility that Ferrari could still emerge on top.
“You can only feel comfortable if you can use those tokens effectively,” Wolff told Motorsport.com.
“At the moment we are pretty flat out in our developments, but we haven't worked out yet when and how many tokens we are planning to use.
“It is sometimes misunderstood: one token does not simply mean more performance. It is a more complicated formula than that.”
Wolff also warns that Mercedes' rate of progress in being able to find performance steps with its engine may be slowing – and that its fight with Ferrari could now rest on being able to deliver car improvements.
“In engine regulations it is a law of diminishing returns,” he said. “In theory, our learning curve is going to flatten out a bit and everyone who was late [with development] has a steeper learning curve than ourselves. At a certain stage these two trajectories will meet.
"Nevertheless, we have a really great group of engine people, who set themselves very ambitious targets – and new targets regularly.
“The same applies to the aero department, to vehicle performance, and quality control throughout the whole factory. It seems there there is a philosophy – for whenever you meet people in composites or manufacturing, in R&D, in the race team, it is a constant push for excellence.”
Engine tokens remaining after Hungarian GP: