Formula 1's governing body, the FIA, has issued a new technical directive aimed at ensuring parity between manufacturer works teams and their engine customers.

While it is always to be expected the teams which develop their own power units or have a technical partnership with a manufacturer will have an advantage over those who pay and plug in, F1's rule makers have addressed concerns customer teams were being deliberately held back.

Under Appendix 4 of the sporting regulations, it is written that all engines supplied must be identical in terms of hardware but now this new directive addresses the use of special engine modes, such as in qualifying.

"Appendix 4 and the dossier system ensure that all power units supplied by one manufacturer are identical in all respects, but we have good reason to believe that this may not be the case," the FIA claimed in the directive quoted by Motorsport.com.

"Whilst the dossiers for each team may be identical it would appear that some are being operated in a different way to others being supplied by the same manufacturer.

"It is therefore our view that all power units supplied by one manufacturer should be identical, not only in terms of the dossier for each team being the same, but we also feel they should be operated in an identical way."

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This means software, i.e. the engine modes, and fuel and oils used in the works team of, for instance, the Mercedes, must be the same as those inside the Force India and Williams.

The only time this is not the case is when a customer has elected to use an older specification engine, as Ferrari did with Toro Rosso and Sauber in 2016 and 2017 respectively.