MG is preparing two smaller diesel engines to sit alongside its new 1.9-litre motor in its growing line-up, while a more efficient version of the larger diesel is also planned.
The new diesel jointly developed at MG's facility in Longbridge and with its parent firm SAIC in China produces 148bhp and 258lb ft of torque, but emits a relatively high 139g/km of CO2 in the MG 6.
The new design will be adapted to create a pair of smaller engines: a 1.2-litre three-cylinder motor that will be used in the MG 3 the company's Fiesta-rivalling supermini due next year and a 1.6-litre four-cylinder version.
The larger of the two engines is being designed for the MG 5, a Ford Focus rival due in the first half of 2014. However, it is unlikely to be ready for the car's launch, and MG is said to be exploring the possibility of using an engine from a third-party supplier most likely Peugeot-Citroen or General Motors in early models.
The 1.9-litre unit also has the potential to run with less power and torque, and a narrower power band, to deliver CO2 emissions as low as 119g/km.
One senior engineering source said: 'We've taken a decision that it's better to launch with a strong diesel engine one that still delivers a useful CO2 figure, but with pace than to bring out an ultra-efficient motor that's a little less flexible.'