An insert device may include a body coupled with an engine cylinder head. The body has an interior surface shaped to receive and engage a distal tip of a fuel injector. The body has gas conduits and mixture conduits with gas conduits extending from inlets along an exterior surface to outlets that intersect the mixture conduits. The mixture conduits extend from inlets along an interior surface of the body to outlets on the exterior surface. The gas conduits are positioned to direct gases outside of the body into the mixture conduits. The mixture conduits are positioned to receive fuel from spray holes of the fuel injector. The mixture conduits can entrain the gas with the fuel into a fuel-and-gas mixture that is directed out of the outlets of the mixture conduits and into a combustion chamber of an engine cylinder.

A device supplies water into a high-pressure fuel pump of a motor vehicle internal combustion engine, wherein the water is admixed to the fuel in the inlet region of the high-pressure fuel pump in a controlled manner by a metering valve, and wherein the device is designed to guide the water at least from a part of a supply line back to the storage container. When viewed in the flow direction from the storage container to the high-pressure fuel pump, a shut-off valve is provided in the supply line upstream of the metering valve, and the supply line is designed to elastically deformably change its volume in a line section positioned between the valves. In an operating method, wherein, after the parking of the motor vehicle in conditions that make it possible for the liquid that is at risk of freezing to freeze, and/or after delivery of the liquid to the high-pressure fuel pump, and with a suitably adjusted upstream fluid pressure, the metering valve is opened and remains open until a portion of the fluid in the section of the supply line leading from the metering valve to the high-pressure fuel pump flows out through the metering valve.