The three customer teams using Mercedes power units in Formula 1 will not receive the latest specification engine this season.
According to Autosport, due to the inability to produce enough of the latest specification parts, Sahara Force India, Williams Martini Racing and the Lotus F1 Team will be forced to continue with the early versions of the engine until the end of the season.
Only the Mercedes AMG PETRONAS team have been able to use the latest version of the engine, with Lewis Hamilton set to use his second such engine in Russia, which will be his fourth power unit of the season.
As well as Hamilton, the remaining Mercedes-powered drivers are all set to move onto their fourth power unit at Sochi, apart from Nico Rosberg and Nico Hulkenberg, who are already using their fourth units.
The delay in introducing the new power units to the customer teams means it will be pre-season testing in 2016 before the customer teams will be able to run with the upgraded units.
