The FIA is convinced that the performance of the top three engines in Formula 1 has now converged to be within three tenths of a second.
F1's manufacturers and the FIA agreed to work towards engine parity in a meeting at last year's Spanish Grand Prix.
Following detailed analysis of the performance of the four different power units during the first three events of the 2017 season, the FIA's estimates suggest Mercedes, Ferrari and Renault are within the 0.3s bracket that it was agreed should apply to the leading three engines on a theoretical lap of the Barcelona circuit.
F1 race director Charlie Whiting said the process was "far more complicated" than it might sound as it uses "a very detailed methodology for simulating this based on all the data that only we have".
The results were announced to teams at this week's F1 Strategy Group meeting.
It is understood the FIA's conclusion has not pleased Red Bull and that during the meeting it queried whether its supplier Renault was within the 0.3s margin.
Whiting said any objections were not valid because the FIA had strictly followed the procedures agreed with the manufacturers.
"It is something that they all signed up to and agreed with the methodology - and that is the most important thing," he said.
"The four engine manufacturers sat down for hours and hours and thrashed out this rather complex method.
"Obviously this was done among the power unit manufacturers not the teams.
"I think there may be a little element of surprise about this.
"But we do have convergence as defined by this system.
"We cannot renegotiate it.
"It is something that has been in place for a year or so now.
"They have all known how it was going to be done and that is how it has been done. And those are the results."
The agreement to only cover the top three manufacturers means there is no scope for any freeing up of the rules to help Honda out, which McLaren had hoped for.
"It wasn't a matter of helping anybody," said Whiting when asked about the Honda situation.
"It was a matter of establishing that the measures that had been introduced, losing the tokens and all those sorts of things that were aimed at helping convergence, had worked."
Whiting said the FIA will continue to monitor the performance of the engines over the remainder of the campaign to ensure that they stay within the 0.3s window.