With the implementation of alternative fuel sources on the minds of many, diesel is now under the microscope more than ever. Although diesel-powered vehicles have been around for a long time, gasoline is still the primary fuel source for most North American vehicles. Why has diesel not been used as a fuel source in more vehicles? Which is better for the environment? These are questions that are being asked more frequently as the search for alternative fuels is weighing heavily on more people's minds.

Gasoline vs. Diesel

It turns out that gasoline is more volatile than diesel, not because of what its base consists of, but because of the additives it contains. In addition, vehicles that use diesel tend to be more fuel-efficient and produce less greenhouse gasses. In that respect, diesel is more environmentally friendly. Diesel actually produces 15% more in greenhouse gasses than gasoline when compared by the litre rather than the gallon. Yet it is through the 20-40% improvement in fuel economy over gasoline that offsets the higher emissions per litre. In actuality, the carbon dioxide emissions are considerably less than gasoline, but diesel does contain 2,778 grams of carbon per gallon, whereas gasoline contains 2,421 grams per gallon. But, again, it is the fuel economy of diesel that accounts for the smaller rate of carbon emissions.

Then again, diesel fuel contains larger quantities of sulfur. The United States has what is considered to be the dirtiest diesel, but as of June 1, 2010 this is going to be different. U.S. diesel fuel has a lower measure of ignition quality. This means that when it is cold outside, ignition performance is poor and can result in higher emissions. This is why you see truck drivers idling their trucks all night long in cold weather rather than risk a troublesome start in the mornings.

But, the sulfur in the diesel that is emitted during cold ignitions and long engine idling is still harmful to the environment because the sulfurs prevent the control of diesel particulate emissions through diesel particulate filters. This is changing, though, since new advanced technologies such as nitrogen oxide absorbers are being developed to reduce these emissions.

As for gasoline, it is the non-aliphatic hydrocarbons as well as carcinogenic additives that avoid engine-knocking that threaten the public's health and the environment. This exposure happens in the case of gasoline leaks and then, of course, there are the carbon emissions we hear a lot about. Leaks occur when trucks begin leaking the gasoline they are carrying, storage containers are not stored properly, and from motor vehicle leakage. The harmful additives in gasoline can get into groundwater and contaminate public water supplies.

However, Dieselization is becoming a more common use of diesel as a fuel in motor vehicles, although it is determined that both diesel and gasoline have harmful effects on the environment. When we look at the carbon emissions of both, we find that diesel will emit more per gallon (or litre), but when you look at how much you have to fill the fuel tank with diesel versus how much you have to fill with gasoline, you will find that the percentage of emissions is offset for diesel, which can be friendlier on the pocketbook. On the other hand, sulfur is emitted by diesel and diesel does not perform as well in cold weather as gasoline, so until 2010 when diesel is cleaned up, gasoline may be slightly more environmentally friendly than diesel in respect to the emissions from automobiles. As for ground contamination, diesel has an edge over gasoline in keeping our world clean.