Diesel D6 Virgin Fuel Oil, commonly known as D6, is a heavy, viscous fuel derived from crude oil through distillation. It is primarily used in power generation, marine applications, and industrial heating due to its high energy density and efficiency. D6 requires pre-heating to 220-260°F (104-127°C) before use, making it unsuitable for smaller engines. As a bunker fuel, it powers large ships and generators, especially in areas lacking access to lighter fuels like natural gas. Recent regulations necessitate further refining to reduce sulfur content, impacting its cost and environmental compliance.