Emissions from today’s diesel trucks and buses are near zero thanks to more efficient engines, more effective emissions control technology and the nationwide availability of ultra-low sulfur diesel fuel. Similar technology will be introduced in off-road construction and agricultural equipment between 2011 and 2014.

The Fuel

Diesel is a petroleum-based fuel with a high energy content - helping diesel go further per gallon than most other alternatives.

• Refiners reduced the sulfur content in diesel fuel by 97 percent. This ultra-clean fuel is important because sulfur tends to hamper exhaust-control devices in diesel engines, like lead once impeded the catalytic converters on gasoline cars. Just as taking the lead out of gasoline in the 1970s enabled a new generation of emissions control technologies that have made gasoline vehicles over 95 percent cleaner, so will removing the sulfur from diesel help usher in a new generation of clean diesel technology.
• Ultra-low sulfur fuel (ULSD) is now available nationwide.

Read DTF's Diesel Fuel Study - Diesel: Fueling the Future in a Green Economy.

The U.S. Energy Information Administration states that few transportation fuels surpass the energy density of diesel.

 Source: U.S. Energy Information Administration, based on the National Defense University.

The Engine

Diesel is the world's most efficient internal combustion engine. It provides more power and more fuel efficiency than alternatives such as gasoline, compressed natural gas or liquefied natural gas. Read more about the history of the diesel engine. 

• Fuel combustion is the primary difference between gasoline and diesel engines. Gasoline engines ignite fuel with spark plugs, whereas diesels ignite fuel with compression. The piston stroke in a diesel engine results in a compression of the fuel air mixture so intense that it combusts spontaneously.
• Advanced new technologies such as electronic controls, common rail fuel injection, variable injection timing, improved combustion chamber configuration and turbocharging have made diesel engines cleaner, quieter and more powerful than past vehicles.

The Emissions Control System

With the introduction of lower sulfur diesel fuel, a number of exhaust treatment systems can further reduce emissions from diesel engines.

• Particulate Traps - collect particulate matter as the exhaust gases pass through and can reduce particulate emissions by 80-90 percent using a catalytic reaction or an auxiliary heating element.
• Catalytic Converters - use a chemical reaction to convert emissions into harmless substances. Some catalysts - such as selective catalytic reduction (SCR) devices and NOx absorbers - focus on nitrogen oxides and can reduce these emissions by 25-50 percent.