Diesel trucks and engines are notoriously linked to the image of belching black smoke as they barrel down the highway. Because of this, people think that diesel engines are dirty and terrible for the environment. Now, there is a grain of truth to this – because diesel engines are the engine of choice for the over-the-road transportation industry, they do contribute the most to urban air pollution as a group. And diesel smoke isn’t just unsightly to look at when you’re stuck behind a big rig on the highway – unburned black smoke carbon particulates (like PCBs) have been shown to contribute to poor air quality and poor lung function in developing children exposed to these particulate regularly over a long period of time.
Black smoke emissions are simply poorly-burned diesel fuel. In an ideal situation, the diesel fuel is burned completely in the engine cylinder, producing carbon dioxide and water to go with over 120,000 BTU of chemical heat energy which the truck engine turns into mechanical work via distance travelled by the vehicle. New diesel engines are quite efficient at doing this. But as the engine ages, its ability to do this is lessened and some of the fuel isn’t completely burned. Incompletely burned fuel essentially appears as soot-like particles – these particles are tiny balls of polymerized (cooked) carbon and other elements. A diesel engine belching black smoke is a diesel engine that isn’t completely burning the fuel.
What causes diesel engines to do this? Build-up of deposits in critical areas of the engine, to start with. Diesel engines are more prone to deposit build-up because a) diesel fuel doesn’t burn as cleanly as gasoline and b) diesel fuel from the refinery doesn’t have as many deposit-controlling additives added to it as gasoline. Both of these mean dirty diesel engines are much more likely to accumulate deposits in injectors, on valves and in combustion chambers and on pistons. Deposits in these critical areas reduce the engine system’s ability to burn all of the fuel completely, and you get black smoke particulate as a result. Not only this, but diesel engines also last a lot longer than gasoline engines, and the older an engine is, the more likely it has significant deposit build-up inside of it.
Diesel fuel that has been improperly stored (oxidized) or contaminated with either water or microbes is also much more likely to burn incompletely and produce black smoke as a result.
Diesel engines have certainly been engineered in recent years to try to minimize this long-standing problem. Many big rig trucks have “particulate traps” to try and catch as much of this black smoke particulate as possible. These traps accumulate some or all of the soot and have to be emptied every so often – the emptied carbon is used in other applications or is burned or disposed of in environmentally-friendly ways.
Fuel additives are also a cost-effective way to reduce or elimi
nate black smoke, especially from engines that have significant deposit build-up. A multi-function treatment like Bell Performance Dee-Zol not only will reduce the amount of particulate resulting from incomplete fuel combustion but will also clean and remove the deposits contributing to the inability of the engine to full combust all of the fuel. A good multi-function treatment like Dee-Zol should be able to accomplish this for pennies per gallon treat cost.
This post was published on October 20, 2010 and was updated on February 12, 2015.