A PRACTICAL supercar is an oxymoron. But not to BMW, which unveiled the new M3 Saloon. This is the second four-door in four generations of the M3. Like the coupe, it is powered by a 420hp 4-litre V8 that has 400Nm of torque at 3,900rpm. Redlining at 8,400rpm, the engine is regulated by a six-speed manual gearbox and variable differential. This conveys up to 100 per cent of available power to the wheel with most grip. The M3 Saloon hits 100kmh in 4.9 seconds, only 0.1 seconds slower than the Coupe.