Fuel is any material that is burnt or altered save gas in order to obtain energy.fuel saver releases its energy either through chemical means, such as combustion, or nuclear means, such as nuclear fission or nuclear fusion. An important property of a useful fuel is that its energy can be stored to be released only when needed, and that the release is controlled in such a way that the energy can be harnessed to produce work.

All carbon-based life forms from microorganisms to animals and humans depend on fuel saver and use fuels as their source of energy. Their cells engage in an enzyme-mediated chemical process called metabolism that converts energy from food or solar power into a form that can be used to sustain life. Additionally, humans employ a variety of techniques to convert one form of energy into another, producing usable energy for purposes that go far beyond the energy needs of a human body. The application of energy released from fuels ranges from heat to cooking and from powering weapons to combustion and generation of electricity increase miles per gallon.

Biofuel can be broadly defined as solid, liquid, or gas fuel consisting of, or derived from biomass. Biomass can also save gas be used directly for heating or power known as biomass fuel. Biofuel can be produced from any carbon source that can be replenished rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture increase gas mileage.

Perhaps the earliest fuel that was employed save gas by humans is wood. Evidence shows controlled fire was used up to 1.5 million years ago at Swartkrans fuel saver, South Africa. It is unknown which hominid species first used fire, as both Australopithecus and an early species increase gas mileage of Homo were present at the sites. As a fuel, wood has remained in use up until the present day, although it has been superseded for many purposes by other sources. Wood has a relatively low energy density of 10–20 MJ/kg fuel saver, which is less than half that of save gas.

Recently biofuels have been developed for use in automotive transport increase miles per gallon (for example E10 fuel).