The data indicates that the BMW 6 Series M6 (2004-07) 2-door coupe with a 5.0 SMG auto transmission predominantly features a 5.0-liter petrol engine, with 99.4% of vehicles equipped with this engine capacity. Additionally, almost all vehicles (99.4%) use petrol as their primary fuel, while a very small fraction (0.6%) are bi-fuel gas variants. This suggests that the vast majority of these models are petrol-powered with a consistent engine size, reflecting their performance-oriented nature.