Pictured here is a clean diesel engine for light trucks that was part of Cummins research and development effort from 1997-2004. Supported with funding by the Energy Department, this engine is as clean and quiet as a gasoline engine, while delivering up to 30 percent better fuel economy. | Photo courtesy of Cummins.

America is reinventing its auto industry, making vehicles that can go farther on a gallon of fuel and saving consumers money at the pump. Through investments in advanced vehicle technologies, the Energy Department is positioning the United States to lead in the global auto market. Follow along on during August as we highlight some of the automotive innovations that can be traced back to the Department — from advanced combustion to lightweigting to clean diesel.

With years of technology advancements behind it, the diesel engine is becoming synonymous with fuel-efficient, lower-emission light-duty truck engines, erasing the outdated image of loud, smoky trucks. Helping to change the conversation are Cummins and Nissan. The two companies recently demonstrated that a four-cylinder clean diesel engine could improve the fuel economy of full-sized pickup trucks by 40 percent compared to a 2009 baseline truck powered by a gasoline V8 engine.

Cummins’ work on clean diesel technology for light trucks dates back to a research and development effort from 1997-2004. Co-funded by the Energy Department the project focused on designing a diesel engine that was as quiet and clean as a gasoline engine yet 30 percent more efficient. Building on this effort, in 2010 Cummins began working on a diesel engine with an award from the Energy Department for $15 million that the company matched dollar-for-dollar. The project’s goal was to dramatically increase the fuel economy of the typical full-size pickup truck while meeting the Environmental Protection Agency’s 2017-2025 emissions standards.

To improve the fuel economy of the V8 gasoline engine (also called an eight-cylinder engine) powered pickup truck and maintain the truck’s performance, Cummins developed a four-cylinder diesel engine that is half the size of the original engine. In addition to downsizing the engine, researchers used aluminum in the engine block to make it lighter and incorporated a unique emission control system — commonly referred to as an aftertreatment system. Cummins then partnered with Nissan to integrate the engine into the Titan truck and demonstrate the fuel economy improvements. Over several months, the companies ran multiple tests in the lab and on the road to ensure engine compatibility with the vehicle’s emissions system and controls, while also making sure it could meet consumer expectations for power, comfort and noise.

The result of the partnership: A four-cylinder diesel engine with comparable performance to an eight-cylinder gasoline engine, which gets an additional 7-10 miles per gallon on average. Plus, it’s compliant with new emissions standards — an important element in cutting our air pollution in the U.S. If all light trucks and SUVs used an engine like this, Americans would reduce the nation’s on-road transportation greenhouse gas footprint by about 10 percent.

Because the Cummins clean diesel engine holds strong promise for helping Nissan meet future emissions and fuel-economy standards, Nissan is independently taking the engine a step further, testing it in the company’s mid-size truck, the Frontier. Adapting the engine for use in the Frontier, Nissan showed a 35 percent increase in fuel economy compared to a Frontier powered by a V6 gasoline engine, while maintaining the original vehicle’s payload and towing capacity.

The Cummins and Nissan project is just one example of how the Energy Department is working to improve the fuel economy of light-duty trucks — a vehicle type that is becoming increasingly more popular for consumers. For more on the Energy Department’s clean diesel engine work, visit the Vehicle Technologies Office website.