Diesel fuel explained Diesel and the environment

Diesel fuel engines

Diesel fuel (refined from crude oil) produces emissions when it burns. As a result, diesel-fueled vehicles create emissions, such as ground-level ozone and particulate matter. The U.S. Environmental Protection Agency (EPA) established standards for the sulfur content of diesel fuel and for emissions from new diesel engines.

Freight truck with diesel engine

Source: Stock photography (copyrighted)

EPA fuel standards require a major reduction in the sulfur content of diesel fuels. To meet the EPA standards, the petroleum industry is producing ultra-low sulfur diesel (ULSD) fuel, a cleaner-burning diesel fuel that contains a maximum sulfur concentration of 15 parts-per-million (ppm). Most of the diesel fuel now sold in the United States for use in vehicles is ULSD fuel.

The EPA also established emissions standards for diesel engine highway vehicles for model year 2007 and later. These engines are designed to operate only with ULSD fuel. Using ULSD fuel and advanced exhaust emission control systems can reduce vehicle particulate emissions by up to 90% and emissions of nitrogen compounds (NOx) by 25% to 50%. ULSD fuel helps reduce emissions in older engines as well.

Carbon dioxide (CO₂) emissions

In 2025, diesel (distillate) fuel consumption accounted for about 24%, or 452 million metric tons of total U.S. transportation sector CO₂ emissions and about 9% of total U.S. energy-related CO₂ emissions.