A fuel-saving device for treating a fuel includes at least one pyroelectric element to be in contact with the fuel. The at least one pyroelectric element includes a high molecular polymer substrate and a plurality of polarized pyroelectric particles dispersed in the polymer substrate. The polarized pyroelectric particle has infrared absorption peaks at wavenumber ranging from 430 cm.sup.1 to 980 cm.sup.1 and from 1600 cm.sup.1 to 2700 cm.sup.1.

The use of ultrasound or acoustics applied at a level below that which causes cavitation to control the energy balance between particles and the liquid phase in a metastable liquid.

The use of ultrasound or acoustics applied at a level below that which causes cavitation to control the energy balance between particles and the liquid phase in a metastable liquid.

A fluid supply device for improving combustion efficiency is provided. The fluid supply device includes a controller and a fluid supply unit coupled to the controller. The fluid supply unit includes an outer housing and a container body having a resonance material, wherein the container body is configured in the outer housing and has a containing space for accommodating a target liquid, and the resonance material is configured adjacent to the target liquid. The resonance material has an infrared ray wavelength to rearrange molecules of the target liquid in the container body to small molecules to increase the combustion efficiency of an internal/external combustion machine, and the controller can adjust the supply volume of the target liquid according to a predefined rule based on an obtained information from the fluid supply unit and/or the internal/external combustion machines, so that the internal/external combustion machine can achieve the best combustion efficiency.