What is Clean Diesel?

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About Clean Diesel


Diesel moves approximately 70 percent of the nation's freight tonnage, and nearly all highway freight trucks are powered by diesel engines.

Today, there are 711,000 trucking companies that rely on 3.5 million drivers to deliver for the U.S. economy. Three out of four trucks on the road are powered by diesel and 97 percent of the large over-the-road Class 8 trucks are diesel. Over the last 20 years, emissions from heavy-duty diesel trucks, buses and other vehicles have been reduced by 95 percent for nitrogen oxides (NOx) - an ozone precursor - and 90 percent for particulate emissions. It would take 60 new trucks to generate the same emissions as a single truck manufactured in 1988!

60 trucks infographic

 2021 HD Benefits Infographic


The newest generation of clean diesel vehicles is a growing portion of the total diesel commercial truck population. About half of all diesel commercial vehicles on the road in the United States is now equipped with the newest technology clean diesel engines - those manufactured beginning in model year 2010 that have near zero emissions of NOx and particulate matter.

A new generation of clean diesel technology is fueling those trucks that reduce emissions including greenhouse gas (GHG) emissions while saving fuel as more truckers invest in new technology clean diesel engines.

Over the past couple of years there has been a lot of speculation about a revolution in fuels and technology in the trucking industry. The 2020, year-end U.S. truck vehicles-in-use data shows that almost about 75 percent of all commercial vehicles are powered by diesel engines, and among the largest trucks (Class 8) diesel vehicles-in-use accounted for 97 percent of the overall population. So it appears that the ‘revolution’ is that truckers are choosing new clean diesel truck technology in increasing numbers over all other fuel sources.

In fact, the Fuels Institute predicts that diesel will continue to be the standard powertrain and fuel powering commercial vehicles in the future. Diesel also provides a unique technology platform suitable for expanded use of hybrid powertrains and lower-carbon renewable fuels - both strategies for reducing GHG emissions that will continue to expand in the future.

Diesel power is the driving force today of goods movement by truck in our economy and diesel will play a central role in efforts to reduce fuel consumption, promote energy security and lower GHG emissions in the years ahead. 

Clean Diesel Progress

While continuously making commercial trucks more fuel efficient, diesel engine and truck manufacturers have also been making them dramatically cleaner, a significant accomplishment considering that increased fuel efficiency and lower emissions are near opposite and competing forces in diesel engine design. In fact, diesel vehicles manufactured after 2010 achieve an average 5 percent improvement in fuel economy resulting in petroleum reduction equivalent to 5.8 billion barrels of crude oil. An owner of a single Class 8 truck powered by the latest clean diesel engine can expect to save about 2,200 gallons of fuel each year compared to previous generations of technology. This reduces greenhouse gas emissions by nearly 30 tons.  Additional fuel-saving strategies are being developed to improve efficiency, including further engine refinements, vehicle aerodynamics and expanded use of hybrid technology for some applications.

New diesel vehicles are increasing their penetration in the marketplace because in part, due to fuel efficiency requirements of Phase 1 of the U.S. Environmental Protection Agency (EPA) and National Highway Traffic Safety Administration (NHTSA) Fuel Efficiency standards that went into effect in 2014 and the more stringent Phase 2  rules that kicked-in in 2021. The more stringent Phase 2 rule is expected to eliminate over 1 billion tons of greenhouse gas emissions between 2021 and 2027.  More efficient diesel trucks will deliver the overwhelming majority of these benefits even as zero-emissions technologies are expected to hit dealer lots over the lifetime of the rule.

While diesel trucks will become more efficient diesel will also become cleaner.  Truck and engine manufacturers and stakeholders are hard at work developing closer-to-zero emissions solutions for oxides of nitrogen and fine particles and are working in support of future standards with the U.S. Environmental Protection Agency through the Cleaner Trucks Initiative

For additional information about engine certification standards and government regulations, visit the Truck & Engine Manufacturers Association (EMA) website.


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