Abstract: A process and a device for producing a finely distributed fuel mist, especially for preparing an easily burnable fuel-air mixture for the heater (25) of a motor vehicle. In a chamber (1) which is partially filled with a fuel (3), an ultrasonic oscillator (2) is immersed in the liquid fuel (3) and a fuel column with an exposed fuel surface (4) is formed above the ultrasonic oscillator (2). The ultrasonic oscillator (2) is operated with a frequency such that extremely small fuel particles (5) are detached at the surface (4) of the and a fuel mist is formed in the chamber (1). In a heater, the device in located in an air flow stream which creates a negative pressure that draws the fuel mist out of the chamber opening (6).