Clean Diesel

Clean Diesel Technology Vehicles

2016 Audi R8 V12 TDI Clean Diesel

The Ultimate Information Guide to Understand Clean Diesel Vehicles

Traditional diesel fuel is highly efficient, but also known as a notoriously dirty pollutant. Clean diesel refers to a new approach to diesel fuel, which creates a new cleaner version of diesel fuel, along with an accompanying emission control system. The goal behind this technology is to harnesses the benefits of diesel efficiency, while remaining environmentally friendly. Below, we explore what this new technology is, how it works, as well as the pros-and-cons.

What Are Clean Diesel Vehicles?


Clean Diesel Vehicle Definition

Clean diesel technology (also called Ultra Low Sulfur Diesel or ULSD vehicles) refers to an overall approach in modern diesel vehicles that combines Ultra Low Sulfur Diesel fuel, with new highly efficient diesel engines, and emission control measures. The result of clean diesel technology is an generally low emission and highly fuel efficient producing engine. Ultra Low Sulfur Diesel fuels are able achieve drastically reduced sulphur contents by refining out much more of the particulates that are present in older diesel fuels.


Clean Diesel Cars Explained

Sulphur, which is a natural part of crude oil from which diesel fuel is derived, is one of the key causes of particulates or “soot” emitted from diesel exhaust. Particulates are the main culprit of diesel engines' black exhaust pollutants.

Clean diesel technology aims to drastically reduce the “soot” output of diesel engines by using Ultra Low Sulfur Diesel fuels, modern highly efficient engines, and stringent emission control measures. One might ask "if diesel is such a natural polluter as-is, why go through the hassle to clean it up so much?" The answer lies in the fact that diesel has the highest energy density among all commonly used transportation fuels, which equates to more energy per gallon than its alternatives.

Note: Ultra Low Sulfur Diesel should not to be confused with biodiesel. Biodiesel is diesel fuel derived from biological ingredients such as plant oil or animal fat and usually blended with standard diesel fuel.

2016 Audi R8 V12 TDI Clean Diesel
2016 Audi R8 V12 TDI

How Do Clean Diesel Engines Work?

Both gasoline (petrol) and diesel fuels are used in internal combustion engines for the conversion of chemical energy into mechanical energy. The primary difference between the two is the way fuel in which combustion is accomplished:

  • A gasoline engine takes in a mixture of gasoline and air, compresses it and ignites the mixture with a spark plug.
  • A diesel engine takes in air, compresses it, and then injects fuel into the cylinder. When the fuel contacts the hot air, it ignites.
The diesel engine method is possible because diesel engines produce much greater compression ratios and diesel fuel is more stable than gasoline. Typical gasoline engines have a compressession ratio no higher than 12:1. Diesel engine compressesaion ratios are around 14:1 and go as high as 25:1.

How do hydrogen fuel-cell cars work diagram?
The following technologies are core components to clean diesel technology powered vehicles:
  1. Ultra Low Sulfur Diesel (ULSD) - Ultra Low Sulfur Diesel is a petroleum-based fuel just like regular diesel fuel, but cleaner. ULSD fuels are significantly more refined so that their sulphur content is reduced down to atleast 15 parts per million (ppm) of sulphur. To put this in perspective, the standard highway-use diesel fuel sold in the United States contains an average of 500 parts per million (ppm) of sulphur. This equates to ULSD fuels containing 97 percent less sulfur than other diesel alternatives.

  2. Clean Diesel Engine - Modern clean diesel engines provide more power and fuel efficiency than alternative engine-types such as gasoline, compressed natural gas or liquefied natural gas. By significantly lowering sulfur levels in diesel fuel, engine compression and ignition processes have become cleaner, providing noticeable gains in torque. Other technologies in clean diesel engines include rail fuel injection, variable injection timing and improved combustion chamber configuration. The combination of these clean diesel engine technology improvements have resulted in cleaner, quieter, and more powerful diesel engines.

  3. Emission Control Systems - Clean diesel emission control systems have undergone significant advancements. New Selective Catalytic Reduction systems reduce NOx using diesel exhaust fluid to neutralize the toxic exhaust gases and turn them into safer output. Exhaust gas re-circulation technology sends a portion of the exhaust gases back into the combustion chamber. This, lowers the combustion temperature to reduce the formation of NOx. Finally, particle filters in emissions control systems filter out particles to reduce the number of particulates released.

Clean Diesel Pros and Cons


  • Fuel Efficiency - Because of their unique engine design, diesel engines are typically 20 to 40 percent more fuel-efficient than comparable gasoline engines. This is because petroleum based diesel fuel has the highest energy density among transportation fuels, which equates to more energy per gallon than its alternatives. This results in less frequent visits to the pump to fill up.

  • Increased Power - Diesel powered engines provide more torque, which is why they are often used in commercial transport application, towing, and trucks. When paired with advanced engine technologies, the favorable gains in torque have generated consumer interest in placing diesel engines in passenger cars.

  • Value Retention - Diesel engine vehicles tend to hold their value better than their gasoline (petrol) counterparts. This is partly because fewer diesel vehicles are introduced into the market, which creates a supply constraint on demand. During periods of high gas prices, favorable fuel efficiencies also help drive strong demand for these vehicles.

  • Refueling Options - One of the largest problems facing gasoline-alternative vehicles is the lack of public charging/refueling infrastructure. While it is true that not all gas stations offer diesel fuel, over 50% of all gas stations across the united states do. Thus, the odds of finding a station to refuel your diesel vehicle are significantly better than trying to recharge an electric vehicle or refuel a hydrogen fuel cell vehicle.

  • Reliability - Diesel engines are generally more reliable than gasoline engines. Reasons behind this include the fact that diesel engines are built-heavier than gasoline engines to sustain the added stress of haveing a higher compression, they do not have ignition systems, and the exhaust systems last longer because diesel fuel exhaust is not as corrosive a gasoline engine exhaust.


  • Sticker Price - Those shopping for a clean diesel vehicle will quickly notice the difference in price between the gas and diesel version of the same car. This is due to the fact that diesel vehicle components cost more, diesel vehicle engines are built with heavier grade components, and there are fewer actual diesel vehicles introduced to the market.

  • Limited Selection - Not so much in Europe, but in the United States, there is a limited selection of diesel vehicles to choose from, for prospective vehicle shoppers to choose from. Various industry reports assert that Volkswagen makes up nearly a quarter of all diesel sales in the United States, with its Volkswagen and Audi diesel consumer vehicles.

  • Emission Quality - Exhaust fumes emitted from a typical diesel engine are "dirtier" than comparable gasoline engine exhaust fumes. The emission quality concern is that the sulfur dioxide emitted from the vehicles goes into the atmosphere, where it can combine with water to produce sulfuric acid, thus, produce acid rain.

  • Refueling Options - Specific to the United States, not all gas stations offer diesel fuel. In fact, Business Insider reports that approximately 50 percent of all gas stations in the United States have diesel fuel pumps. For those in the market to purchase a diesel vehicle, it is important to be cognizant of the potential refuelling hurdles when travelling, because not all gas stations will offer diesel fuel.

  • Maintenance Complications - Clean diesel technology vehicles are more technologically more complicated than gasoline powered vehicles. This means that neglected maintenance can be more costly than the same in a gasoline vehicle. For example, if the fuel injection system breaks, it may be more costly to hire a diesel mechanic to get it fixed.