BMW’s alphanumeric naming system puts an even number before 2-door and coupe-styled models and odd numerals preceding vehicles with 4-doors or a more traditional sedan-like design. Coming this fall is the all-new 6 Series Gran Turismo; a quasi-car, hatchback, crossover based upon the recently introduced 5-series. It earns its even number from the fact that its roofline reaches its highest point at the top of the B-pillar, flowing like a …