Teams at Française de Mécanique assembled the site's 300,000th Turbo PureTech threecylinder petrol engine on 19 March.
Globall, the engine is fitted on the Peugeot 208, 308, 2008 and 3008, the Citroën C3, C4, C4 Cactus and C4 Picasso, and the DS 3 and DS 4.
It cuts fuel consumption and CO2 emissions by an average 18% compared with the naturally aspirated EP engine, already the market's top performer.
The smaller, lighter Turbo PureTech petrol engine offers a remarkable level of driving pleasure and performance for a model in its cylinder class.
In June 2015, it was named Engine of the Year in the 1l to 1.4l category at the International Engine of the Year Awards. The accolade recognises both the technology and the performance of this market-leading powerplant.
Production of the Turbo PureTech engine began in March 2014 at the Française de Mécanique plant and a total of 6,450 units are now manufactured weekly by four teams. .
Commenting, Denis Martin, Operational Director Europe, said: "Our PureTech petrol engine is a key factor in the success of the models it is fitted on. Given current trends in the petrol/diesel model mix, the performance of this excellent threecylinder engine gives PSA a competitive edge that our front-line teams can leverage to win market share".