By 2040, the go-to fuel still will dominate the commercial truck fleet, and it’s getting cleaner.


By Ezra Finkin

A recent headline, “Daimler, Volvo Show Hydrogen Is Here, Diesel Has a Sell-By Date,” touts the new interest in hydrogen for heavy-duty commercial trucks from some leading manufacturers. Today, over 90% of commercial vehicles are powered by diesel technology. Fast forward 20 years from now, and trucks most likely will be powered by a diverse mix of fuels and technology. Some may be powered by hydrogen and fuel cells, some by battery-electric and some by operating on renewable natural gas or renewable diesel fuel. According to many sources, however, rather than having a “sell-by” date, diesel will remain the dominant technology moving the nation’s freight for decades to come.

A variety of analysts and researchers have explored the future trucking fleet composition, and by 2040 diesel is still at the top when it comes to the Class 8 truck fleet.

  • Bloomberg New Energy Finance, which traditionally publishes an upbeat forecast for electrified cars and trucks, estimates that only 19% of the heavy-duty commercial truck fleet in the U.S. will be electrified by 2040—meaning 81% of heavy-duty trucks will be powered mostly by diesel and some natural gas.
  • IHS Markit estimates that 80% of commercial truck sales in the U.S. will be powered by diesel by 2040.
  • The Fuels Institute estimates that, under aggressive uptake of zero-emissions technology in commercial vehicles, diesel will make up 65% of heavy-duty truck sales and 86% of the fleet by 2040.
  • The International Council on Clean Transportation notes that there is only one manufacturer of a zero-emissions Class 7 and 8 truck available in the marketplace today, albeit with limited range, while others are still in pre-production phase. ICCT notes that heavy-duty zero-emissions trucks will overtake diesel in sales during the next two decades.

Each of these forecasts makes considerable assumptions about the success of new technology in the commercial marketplace, the price and availability of both diesel and new alternative fuels and many other factors. In the meantime, progress in reducing emissions, fuel consumption and greenhouse gas (GHG) emissions from diesel technology continues, with new milestones set for the future—all good news for the climate and clean air.

Much like passenger vehicles, commercial vehicles are subject to stringent fuel-economy and greenhouse-gas emissions standards that have been phased in since 2014, and more-stringent rules take effect this year. Over the lifetime of these rules, more fuel-efficient trucks will have eliminated more than one billion tons of greenhouse gas emissions between 2014 and 2027 according to EPA’s Phase 1 and 2 rules. While there will be emerging zero-emissions trucks for sure, they will be in fractional percentages of the total fleet market, making most of the benefits delivered by trucks fueled by diesel.

Much more efficient diesel trucks are already generating big fuel savings and climate benefits. According to Fleet Advantage, a business consultancy that measures real-world fuel economy, a new Class 8 tractor has a 15% fuel economy benefit over a similar 2016 model. This is a substantial benefit that translates directly to greenhouse gas emissions, and as more older diesel trucks are replaced with new ones, these benefits are expected to continue to grow.

While truck, engine and component makers are working to achieve the next level of greenhouse gas emissions reductions and to reduce fuel consumption, they are also committed to reducing emissions from the current generation of diesel even closer to zero. The U.S. Environmental Protection Agency’s Cleaner Trucks Initiative is expected to establish new goals to further lower emissions of oxides of nitrogen (NOx), a smog-forming compound, along with other provisions in the coming years.

Diesel trucks also have the capability of operating on advanced renewable biofuels that drive down greenhouse gas emissions, operating on high-quality blends of biodiesel or 100% renewable diesel fuel. These are fuels that have at least a 50% reduction in greenhouse gas emissions relative to petroleum. With renewable diesel fuel, GHG emissions are reduced by at least 80%. Many fleets are using the fuels today, and in response, a number of leading oil companies announced the planned retooling of petroleum refineries to produce new supplies of renewable diesel fuel. If planned capacity for the fuel equates to actual production, these facilities have the capability to displace all the petroleum diesel fuel consumed in California.

Recent headlines on any new technologies—fuels, new model cars and trucks or consumer products in general—are eye-catching and interesting. Often, however, they leave out an important part of the story. In this case, that diesel technology will continue to dominate the industry and that it will have even nearer-to-zero emissions with lower GHG emissions, as well. These benefits will be vital in the next several decades before alternative fuel vehicle and infrastructure availability arrives at an impactful scale.


Ezra Finkin is the policy director for the Diesel Technology Forum, a nonprofit organization dedicated to raising awareness about the importance of diesel engines, fuel and technology. Diesel Technology Forum members are global leaders in clean diesel technology and represent the three key elements of the modern clean-diesel system: advanced engines, vehicles and equipment; cleaner diesel fuel; and emissions-control systems.