Diesel engines are cleaner than ever before, and in the next few years the diesel industry will virtually eliminate key emissions associated with on- and off-road diesel equipment. This environmental progress is the result of the new clean diesel system - combining clean diesel fuel, advanced engines and effective exhaust-control technology. Learn about what makes diesel clean…

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 new, 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.
• Click here to read our joint statement with the Natural Resources Defense Council (NRDC) describing the significance of this accomplishment.

Looking for diesel fuel in your area? Find clean diesel stations near you. Click here to see the new labels that distinguish a clean diesel pump.

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.