Diesel engines have been a part of the automotive industry for over a century. But after such a long life, are we now in an age where diesel engines will soon play no role?

Diesel engines have always had remarkable efficiency and widespread applications. From cargo ships and trains to airplanes, they've driven everything. The US market loved diesel engines in half-ton trucks like the Ford F-150, and Chevrolet Silverado.

Today, however, in the face of escalating environmental regulations, diesel's future seems clouded. Scandals like Dieselgate, involving Volkswagen have contributed to its downfall. The global push to reduce CO2 is driving automakers towards electrification. But that isn't an easy feat to achieve either.

Diesel Engines Offer High Efficiency

It was in the late nineteenth century that one man's pursuit of efficiency led to the development of compression ignition. Rudolf Diesel patented the design in 1892, and by 1897 he had successfully created the first diesel engine prototype. This engine operated at better than 26 percent efficiency, and a year later, Diesel was a millionaire.

The compression engine is a technology that extracts exceptional energy from fuel. They were originally used as a more efficient replacement for stationary steam engines. Diesel engines soon became popular for their high efficiency and lower fuel consumption. Per liter, diesel contains more energy than petrol. Since the 1910s, people started using them in submarines and ships. Use in buses, trucks, heavy equipment, electricity generation plants followed later.

Diesel engines flourished in Europe and other parts of the world. But in North America, they struggled to gain widespread traction. The reason was the availability of plenty of affordable gasoline. However, German manufacturers like Mercedes-Benz and Volkswagen tried to sway North American consumers. For instance, in 2019, Mercedes-Benz announced the C300de, a diesel-hybrid powertrain for the C-Class. But this entailed higher production costs and limited fuel price differences.

There was one exception: pickup trucks. These vehicles need more torque than average cars, which diesel could offer. Diesel-powered pickup trucks built a dedicated following for their amazing towing capacity.

Rise and Decline of Diesel Engines In Light Truck

The diesel engine thrived in the light truck segment. Chrysler introduced Cummins straight-six diesels in Dodge Ram pickups in 1989. These became a massive hit. Cummins diesel engine, as seen in Ram Trucks, is still one of the most reliable engines. Customers loved these pickups, particularly those seeking impressive towing capabilities.

In fact, in the last thirty years, almost all major manufacturers installed diesel engines in half-ton trucks. Smaller diesel options followed only due to the pressure for better fuel economy.

Related: 10 Best Diesel Engines For Pickup Trucks

Despite their initial popularity, there were a few challenges. Strict EPA emissions regulation was one of them. Automakers had to install complex after-treatment systems. Clean diesel technology called for innovation. These in turn made the trucks expensive.

Another major challenge was (and still is) the rising cost of diesel fuel. The price began eating up the fuel efficiency benefits of diesel engines. Combined, these reasons reduced the popularity and demand of diesel-powered trucks in the US.

Diesel Engines Still Thrive In Developing Economies

Diesel engines face challenges in the USA, but they've thrived in Europe for a long time. Countries like France and Germany even incentivized diesel vehicles early on to reduce CO2 emissions. In recent years, however, the perception has changed. Germany recently allowed for bans on diesel vehicles. Diesel usage has dwindled to only commercial vehicles and long-distance travel.

These segments of the industry still prefer diesel engines due to the clean diesel tech. These are a set of emissions control measures to reduce the impact on air quality. Modern engines use diesel particulate filters (DPF), and after-treatment systems in their exhausts. This helps keep the emissions levels in check.

Related: 10 New European Cars That Show Diesel Is Still A Fuel Source Worth Considering

Diesel engines are still used in heavy-duty applications, especially in semi-trucks. These vehicles need the high range and durability that only diesel engines offer. The need is to haul heavy loads over long distances, which requires high torque and fuel efficiency. Diesel has that covered, for the time being. In fact, diesel engines make refueling really convenient as well.

Even in this segment, however, the picture is fast changing. Hybrid diesel powertrain and alternative fuels are making their way in here as well. If we talk about complete electrification, however, this is a segment of the automotive market that can take longer than others.

In developing Asian and African economies, the case is different. Diesel engines in cars continue to be a popular affordable choice in countries like India. Major manufacturers continue to offer a diesel variant for most entry-level cars. Despite this, concerns about diesel's impact on air quality have helped promote alternative fuels and tech.

The Dieselgate Scandal Shook The Automotive Industry

It is worth noting that diesel engines have suffered a tarnished reputation. The Dieselgate scandal of 2015 involving Volkswagen was a major shock.

Volkswagen was guilty of deliberate manipulation of emissions tests. The US EPA issued a notice to the automaker, detailing the manipulation. Volkswagen had intentionally programmed turbocharged direct injection (TDI) diesel engines to activate emissions control only during testing.

The scandal shook the entire industry, being the most embarrassing recall in automotive history. More so because Volkswagen had marketed its diesel vehicles as "clean diesel". The scandal affected millions of Volkswagen vehicles sold worldwide. It included the VW Jetta, Golf, Passat, and other models along with Audis, Porsches and other brands under the VW Group umbrella.

The company admitted to cheating on emissions tests. As a result, they had to pay billions of dollars in legal settlements. The scandal led to more scrutiny of diesel tech and emissions testing methods. It even accelerated the shift toward electric vehicles (EVs) and other alternative fuels.

The Future Of Diesel Lies In Innovation

Battery tech is evolving and electrification is fast becoming a norm. Automakers are under pressure to meet stringent emissions regulations. What makes it worse for diesel's future is a loss of dominance in half-ton pickup trucks, due to fuel costs and complex regulations. However, diesel engines are likely to maintain their relevance in heavy-duty trucks.

A hybrid diesel engine can save diesel from complete extinction. Like any hybrid engine, it combines a diesel powertrain with an electric battery system. The goal is simple: improved fuel efficiency and lower emissions. Diesel engines have very clear benefits when compared to gasoline powerplants.

Related: This Test Shows The Main Drawback Of Electric Trucks Vs Diesel And Gasoline Trucks

Hybrid diesel tech is popular in regions with strict emissions regulations. That is why European countries are quick to adopt it. Hybrid diesel tech has gained traction in Asian markets as well.

Another interesting innovation in this regard is the Achates engine, which is an opposed-piston engine, designed to operate using diesel fuel. However, it can also run on alternative fuels like hydrogen. The Achates engine is not a hybrid, but it is possible to integrate it into hybrid powertrain systems. This would further improve efficiency and emissions.

Currently, very few diesel models remain available in the USA. General Motors and Ram offer a diesel option in their full-size pickups. But most manufacturers have ceased to offer diesel variants, in the push for electrification. The future of diesel engines in the USA is at a crossroads, but innovations like the hybrid diesel powertrain or the Achates engine may just save it.