The invention relates to multi-functional additives for a gaseous hydrocarbon fuel based on methane and other simple hydrocarbons, which improve the combustion characteristics of the fuel and thus also are better for the environment and increase fuel economy, and which also improve the fire safety of the fuel. A multi-functional additive for a gaseous hydrocarbon fuel based on methane and other simple hydrocarbons is comprised of trifluoromethane (CF3H) in an amount of up to 10 wt%.