THE M5 has been unleashed.

Official details of BMW's new M5 super sedan have been released, after images and vital details were leaked online a week ahead of their scheduled debut.

The new M5 will be powered by the same 4.4-litre twin-turbocharged V8 engine as the brand's X5 and X6 M models, following a trend from manufacturers to downsize their engines in order to save fuel.

Despite the smaller engine (the existing M5 was fitted with a 5.0-litre V10 powerplant) the new super sedan will produce a few extra kilowatts over BMW's M-badged SUV models – 412kW compared to 408kW – about 10% more than its predecessor (373kW).

Torque output from the new 4.4-litre twin-turbo engine doesn't change from the X5 and X6 M models at 680Nm, representing a jump of 30% over the old V10 engine.

The M5's engine sends its power to the rear wheels via a seven-speed dual-clutch automatic, with a manual option a slight chance of making an appearance.

All that power apparently makes for quite a show, with online reports suggesting the M5 will complete the 0-100kmh dash in just 4.4 seconds, with the 0-200kmh sprint taking just 13 seconds. The top speed is limited at 250kmh, but if you plan to do some track days you can choose the M-Drivers Package, which boosts the top speed ability to 305kmh.

The other benefit of the new, more efficient engine is a 30% drop in fuel consumption. The new model uses a claimed 9.9 litres per 100 kilometres, where the old V10 version used 13.0L/100km.

The styling of the new M5 doesn't stray far from that of the concept version unveiled at the Shanghai motor show.