Pilot Fuel

Pilot fuel is the small charge of conventional liquid fuel, usually MGO or marine diesel oil, injected to ignite the main fuel in a dual-fuel marine engine. Methanol, ammonia, and low-pressure LNG (Otto-cycle) engines do not auto-ignite reliably, so a high-cetane pilot is compression-ignited first and its flame ignites the main charge. Pilot fraction ranges from under 1 percent of energy in high-pressure diesel-cycle designs (MAN ME-GI) to 5 percent or more in low-pressure Otto-cycle units. The pilot is fossil-derived unless a renewable distillate replaces it, so it adds a residual carbon and SOx contribution that erodes the well-to-wake benefit of the alternative main fuel.