What is Clean Diesel?


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About Clean Diesel

Why Diesel Isn't Dirty

With a higher degree of certainty than ever before, we can say that diesel is a clean technology.


The Clean Diesel Journey

Diesel is a technology of continuous improvement and that goes for the fuel as well. Ultra-low sulfur diesel fuel has been the standard for both on-highway and off-highway diesel engines nationwide since 2007. By cutting sulfur levels in diesel fuel by 97 percent, immediate clean air benefits accrued - through lower soot emissions from all diesel vehicles and equipment using the fuel (both old and new) by 10 percent. Reducing the sulfur content of diesel fuel is similar to removing lead from gasoline during the 1970s.

Cleaner diesel fuel is the foundation that enabled the development and introduction of a new generation of advanced engines and emission control devices to meet strict “near zero” emissions standards.  

Heavy-Duty Trucks:

Advanced diesel engine designs and emission control technologies were developed to meet strict tailpipe emissions standards for new commercial vehicles manufactured in 2007 and the stricter standard established for 2010.  Thanks to the clean diesel system found on new and newer diesel commercial vehicles, it takes about 60 of today’s trucks to generate the same level of emissions as just one truck manufactured in 1988.  EPA and National Highway Traffic Safety Administration (NHTSA) established a national program to reduce GHG emissions and establish new fuel efficiency standards for commercial vehicles that will increase their fuel efficiency by up to about 40 percent when fully implemented in 2027.  Clean diesel is the primary powertrain that will achieve these goals. 

Those Phase 1 rules are now implemented beginning with model year 2014 and EPA and NHTSA announced proposed rules for the second phase of fuel economy and greenhouse gas emissions reduction from the heavy-duty fleet that would apply beginning in 2021 through 2027 and further reduce carbon emissions.

Construction and Agriculture:

Next up at bat in the clean diesel dugout are off-road equipment. In 2014, new engines that power off-road equipment including construction agricultural equipment are required to meet the similarly strict Tier 4 standards. These requirements kicked in starting in 2015 for much larger engines that power locomotives, marine vessels and other impressively large applications. 

Diesel Cars, Pickup Trucks and SUVs:

The U.S. already has one of the strictest standards in the world regarding clean air requirements for automobiles and light trucks, including diesel models, which are held to the same strict standard as gasoline, hybrid and other competing technologies. While introducing new diesel clean is an accomplishment in and of itself, the industry is not resting on its accomplishments.  Beginning in 2017, a more stringent Tier 3 emissions standard will replace the Tier 2 standard for newly manufactured passenger vehicles. Thanks to over a decade of innovation, clean diesel technology has been developed and deployed to meet these strict Tier 2 passenger vehicle emissions standards.  According to the National Academy of Sciences, these same technologies will be able to meet the stricter Tier 3 standards that phase in beginning in 2017.

Looking beyond the VW crisis headlines, the fundamentals are there for diesel to regain momentum in the passenger market space and auto makers are still committed to diesel as one of the pathways to meet the 52.5 mpg corporate fuel economy mandates looming in 2025. 

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About Clean Diesel Overview

Hot Issues

Weighing in on the Dirty vs. Clean Diesel Debate

Ramanan Krishnamoorti, the University of Houston’s Chief Energy Officer, and William S. Epling of the Cullen College of Engineering, weigh in on the benefits of new diesel technology:

“Those improvements in fuel, engine design and emissions controls technology have resulted in remarkably clean diesel vehicles that maintain their efficiency advantage over comparable gasoline engines and are clearly an important part of the portfolio of solutions to develop environmentally friendly and high efficiency automobiles. Allowing the scandal over Volkswagen’s actions to overshadow the promises of clean diesel engines would be an unnecessary setback in the global push for both energy conservation and cleaner air.”

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