EIGHT years after the highly successful Mercedes-Benz CLS, BMW has finally answered the call with its philosophically identical 6 Series Gran Coupe.

On sale now from $184,800 before on-road costs, the four-door 640i commands a $6500 premium over its two-door Coupe equivalent, but undercuts the convertible version by $9500.

In contrast, the similarly powered 5 Series (confusingly called the 535i) will set buyers back just $115,600.

From September, the 650i Gran Coupe with V8 performance will touch down from about $240,000, ahead of an M6 range-topping barnstormer for 2013.

Obviously the Gran Coupe has the CLS and Audi A7 Sportback in its crosshairs, but BMW also crosschecks the far more expensive Maserati Quattroporte, Porsche Panamera and Aston Martin Rapide as targets.

Standard equipment on even the most basic 640i includes a 10.2-inch screen for the BMW Professional satellite-navigation system, in-car internet and rear camera.

Other standard features include tilt-only sunroof, head-up display, electric power steering, Dynamic Damper Control, adaptive LED headlights with cornering function, heated front seats, keyless entry and start, four-zone climate-control, a rear folding backrest, full-length rear-screen LED brake lights (a BMW-first) and 19-inch alloy wheels.

Unlike most of its foes, the Gran Coupe is technically a five-seater, though even BMW acknowledges that the complete lack of rear-middle legroom means it is more of a ‘4+1’ proposition that requires the occupant to straddle the wide centre tunnel.

The 640i costs some $37,500 and $20,230 more than the equivalent Audi and Mercedes models, and is just $22,100 under the entry-level petrol-powered 7 Series (740i).

A derivation of the 6 Series Coupe and Convertible, with shared nose components ahead of the more raked A-pillars are shared, the imposingly low and sleek German-built Gran Coupe sits on a 2968mm wheelbase – 113mm longer than the other 6 Series models.

Like its two-door sibling, the doors and bonnet are made from aluminium, but the roof is obviously longer and flatter, as well as 24mm higher, for its role as a 4+1-seater grand tourer.

It is 5007mm long (102mm greater than the 5 Series but 65mm shy of the 7 Series), 1894mm wide and 1392mm high, with body stretching devoted to increasing rear-seat legroom over the Coupe.

Aided by a folding rear backrest, boot volume rises from 460 litres (the same as the Coupe) to 1265 litres.

The 1750kg 640i Gran Coupe is powered by the same 3.0-litre straight-six as the Coupe and Convertible.

Employing direct-injection ‘TwinPower Turbo’ twin-scroll forced induction, the power (235kW from 5800 to 6000rpm) and torque (450Nm from 1300 to 4500rpm) outputs are delivered to the rear wheels via a ZF eight-speed automatic Steptronic transmission.

The 0-100km/h acceleration time is 5.4 seconds, top speed is electronically limited to 250km/h, the combined fuel consumption is 7.8 litres per 100km (7.9 if fitted with the optional 20-inch alloys) and carbon dioxide emissions average 182 grams per kilometre.

Consumption is helped by a host of eco measures, including idle-stop, regenerative braking and on-demand ancillary components.

In contrast, the 650i coming in September will boast a 4.4-litre V8 belting out 330kW at 5500rpm and 650Nm between 2000 and 4500rpm, for stats of 4.5s, 8.6L/100km and about 199g/km.

The double-wishbone front suspension is basically a derivation of the X5 SUV’s, which is in turn loosely related to the 5 Series, while the Integral-V multi-arm rear axle is a heavy development of the previous-generation 7 Series.

Single-piston aluminium floating-calliper disc brakes (vented up front) bring the 640i to a fast stop, helped along by the usual swag of stability, traction and cornering controls, as well as BMW’s Dynamic Brake Control, Dry Braking Function, (brake) Fading Compensation and start-off assist systems.

Steering is speed-sensitive electric power-assisted while the standard run-flat tyres are 245/40R19 up front and 275/35R19s at the back.

Finally, except for a different centre console layout in an otherwise identical dashboard, the front half of the interior is shared with other 6 Series variants.

BMW Australia communications manager Piers Scott said “BMW isn’t in the business of talking sales figures”, but suggested the Gran Coupe will sell more than the Coupe and Convertible.