If it's a diesel, it's an alt fuel vehicle by default. Biodiesel blends can be used in any diesel engine; however, it's important to use the blends in accordance with the manufacturers specs. With more and more clean diesels coming on line, keep your eyes peeled for those ULSD pumps too. With fueling stations in all 50 states, it's getting easier and easier for diesels to go cleaner and greener.

Biodiesel is a non-toxic and biodegradable fuel that is made from vegetable oils, waste cooking oil, animal fats or tall oil (a by-product from pulp and paper processing). Biodiesel is produced from these feedstocks through a process called transesterification, by reacting the oil with an alcohol (usually methanol, although ethanol can also be used) and a catalyst (such as sodium hydroxide). The resulting chemical reaction produces glycerine and an ester called biodiesel. The majority of biodiesel is produced by this method.

Compared with conventional diesel, biodiesel combusts better with a higher cetane rating and produces fewer life cycle greenhouse gas emissions (GHG) which contribute to climate change.

Biodiesel blends, a mixture of petroleum diesel and biodiesel, can be used in any diesel engine. As biodiesel can be blended with diesel in any concentration, the blend level depends on economics, availability, the desired emissions level, material compatibility and combustion characteristics.

An increasing number of Original Equipment Manufacturers are endorsing the use of lower biodiesel blends, e.g, 5% in their engines. Some manufacturers now extend warranty coverage for new diesel powered vehicles to use lower blends of biodiesel, provided the fuel meets applicable standards. Some manufacturers also provide vehicles pre-filled with biodiesel blends.

In colder climates, biodiesel tends to lose viscosity, particularly at higher blend levels. To counter this effect, changes to the feedstock source or additives may be needed to address the cold flow properties of this fuel. Research and testing is underway to reduce biodiesel production costs and address cold weather problems.

Biodiesel is considerably less flammable than petroleum diesel, which burns at 50 C (120 F). Pure biodiesel (B-100) does not ignite until 150 C (300 F). The flashpoint (the temperature at which it will ignite when exposed to a spark or flame) of a biodiesel blend falls somewhere between these temperatures, depending on the mixture.

Because biodiesel is a mild solvent it is important to wipe up spills and dispose of rags safely. Biodiesel may deface some paints if left on painted surfaces for a long time.

Hybrids are vehicles of mixed composition basically, an electric motor and an internal combustion engine. Commonly powered by a gasoline engine that generates its own electricity and stores it in an onboard battery, hybrids are a popular choice for awesome fuel economy and squeaky clean emissions.

Pure electrics offer zero emissions and plug directly into a standard AC outlet--while their range is limited, there are a selection of good choices available.

If it's a flexible fuel vehicle (FFV) it can subsist on a diet of E85, gasoline or any percentage of the two. E85 is 85 percent ethanol and 15 percent gasoline, and burns cleaner than gasoline, contributing fewer greenhouse gas emissions.One of the cleanest burning fuels, natural gas is a common retrofit and fleet alternative fuel.

Although there are over 5 million vehicles worldwide powered by natural and compressed gas, in the United States there's currently only one production vehicle available that comes ready to fuel up at any CNG station--but that's not the only way to power up with CNG.

Also known as liquefied propane gas (LPG), propane powers over 10 million vehicles worldwide, with 270,000 of them on the roadways of America. Find out if it's the fuel of choice for your set of wheels.

There are basically two ways to use hydrogen to power a vehicle burning it in an engine or using it as an energy carrier for a fuel cell. While hydrogen fuel cell vehicles are in various states of development, there are a few that have actually hit the roads.