The FIA says it has reached a confidential “settlement” with Ferrari after concluding the analysis of its Formula 1 engine.

Ferrari was under major scrutiny last year for the performance of its engine.

At least one rival believed it was exploiting rules relating to fuel-flow regulations, while other theories emerged over how it might be burning oil to gain performance.

However, no formal protest was ever lodged, Ferrari was never deemed to have broken any rules, and the team maintained its innocence throughout.

The FIA has now released a short statement claiming that “after thorough technical investigations, it has concluded its analysis of the operation of the Scuderia Ferrari Formula 1 power unit and reached a settlement with the team”.

It says the “specifics of the agreement will remain between the parties”.

The Race understands that the investigation into Ferrari’s engine was a long-running affair and a mutual agreement was reached that prevents further resources being spent without necessarily reaching a better conclusion.

However, the FIA believes it has learned enough to reinforce its existing regulations and police them more robustly in the future.

The governing body adds that it and Ferrari have agreed to “a number of technical commitments that will improve the monitoring of all” the engines, including Ferrari’s rival manufacturers Mercedes, Honda and Renault.

This will also “assist the FIA in other regulatory duties in Formula 1 and in its research activities on carbon emissions and sustainable fuels”, the statement says.

It is unclear whether Mercedes, Renault and Honda were aware of this “settlement” prior to the announcement.

When the scrutiny over Ferrari’s engine was at its most intense, the FIA took action through a series of technical directives.

It made clear it would be illegal to manipulate the fuel-flow sensor between the mandated measuring points and briefly exceed the 100kg/h limit between those points.

Then it reminded teams of previous instructions that outlaw burning liquid to improve performance – including, for example, a controlled leak within the intercooler – and requested every team supplied the designation, specification and quantity of lubricants in their engines to give the FIA a reference point for future checks.

Finally, the FIA instructed teams they will be required to add a second FIA-controlled sensor in 2020.