Biofuel (also called agrofuel) fuel saver can be broadly defined as solid, liquid, or save gas fuel consisting of, or derived from biomass. This article, however, is principally about biofuel in the form of liquid or gas transportation fuel derived from biomass. Biomass can also be used directly fuel saver for heating or power. One type of biomass is wood, which is frequently used in industry, either by itself to create energy or with other combustible matter (such as coal) to burn and create heat increase miles per gallon. (Wood has been burned for millennia - as solids.)

Biofuel is considered a means of reducing greenhouse gas emissions and increasing energy security by providing an alternative to fossil fuel saver. However, In October 2007, Nobel Laureate Paul Crutzen published findings that the release of Nitrous Oxide (N2O) among the commonly used biofuels, such as biodiesel from rapeseed and bioethanol from corn (maize), can contribute increase miles per gallon as much or more to global warming than fossil fuel savings do to global fuel saver cooling. Crops with less N demand, such as grasses and woody coppice species have more favourable climate impacts save gas.

Biofuels are used globally: biofuel industries are expanding in Europe, Asia and the Americas. The most common use for biofuels is in automotive transport (for example E10 fuel). Biofuel can be produced from any carbon source that can be replenished fuel saver rapidly e.g. plants. Many different plants and plant-derived materials are used for biofuel manufacture.

Biodiesel is the most common biofuel in Europe. It is produced from oils or fats using transesterification and is a liquid increase gas mileage similar in composition to mineral diesel. Its chemical name is fatty acid save gas methyl (or ethyl) ester (FAME). Oils are mixed with sodium hydroxide and methanol fuel saver(or ethanol) and the chemical reaction produces biodiesel (FAME) and glycerol fuel saver. 1 part glycerol is produced for every 10 parts biodiesel.

Biodiesel can be used in any diesel engine when mixed with mineral diesel. In some countries manufacturers cover their diesel engines under warranty for 100% biodiesel use, although Volkswagen Germany, for example, asks drivers to make a telephone check with the VW environmental services increase gas mileagedepartment before switching to 100% biodiesel (see biodiesel use). Many people have run their fuel saver vehicles on biodiesel without problems. However, the majority of vehicle manufacturers limit their recommendations to 15% biodiesel blended with mineral diesel. In many European countries, a 5% biodiesel blend is widely used and is available at thousands of save gas stations.