NATIONAL HARBOR, MD—A Wednesday morning panel at the ARPA-E summit provocatively asked if the auto industry is about to see ”The End of the Road for the Internal Combustion Engine?”

Though all the panel members agreed that gas- and diesel-based systems are on a path to losing market share, none would admit that the internal combustion engine (ICE) would be completely replaced by the electric vehicle (EV). At least before 2050. So what do industry leaders think will happen or should happen to the evolution of drivetrains in the future?

Perhaps the most interesting perspective came from Amitai Bin-Nun, a vice president in charge of autonomous vehicle innovation for the nonprofit Securing America’s Future Energy, or SAFE. Bin-Nun argued that, without a transition to autonomous vehicles, EVs would not see the mass-market adoption that boosters have been hoping for.

What’s the logic behind that? Essentially, economies of scale. “Most of the companies that are working on autonomous vehicles… see them in the context of a fleet,” Bin-Nun said. Specifically, autonomous fleets have an obvious application in ride-hailing services like Uber or Lyft. Ride-hailing cars are likely to be on the road much more often than individually owned cars, which sit idle in a driveway for the bulk of the day. So for a rationally minded fleet owner, saving on fuel for that constantly moving vehicle will be a huge driver in what kind of vehicle technology is adopted.

That's where EVs come in. Electric cars tend to have a lower total cost of ownership—that is, fuel and maintenance cost less for an EV than for an ICE vehicle.

For individuals, it’s hard to justify purchasing a car that's more expensive initially, even if they'll see small savings on fuel and maintenance many years into the future. But those total cost of ownership savings add up quickly if you manage a large fleet of dozens or hundreds of thousands of cars, and the up-front expense may not be such a concern if you’re a company with easy access to investment cash for capital costs.

That’s why Bin-Nun believes that “absent significant disruption from AV, it will be more than 20 years before EVs are a significant portion of the fleet,” as one of his slides stated.

Efficiency is key

Rachel Muncrief, a program director at the International Council on Clean Transportation (ICCT), said that ICCT’s optimistic outlook shows that 80 percent of vehicles will be electric by 2050. But she cautioned that those numbers still suggest that the world will see the sale of 3 billion more ICE vehicles by 2050, "so it’s very important that those vehicles are as efficient as possible.”

In the ICCT’s model, most of the decarbonization headway that can be made in the realm of gas- and diesel-burning vehicles comes from increasing auto efficiency, although ICCT says some emissions reductions can come from using less energy-intensive fuel extraction (tar sands oil, for example, requires a lot more processing) or from transitioning to biofuels.

Muncrief was supportive of government efficiency standards as a way of pushing automakers to improve their ICE vehicles. She cited proposed EU targets equivalent to 67mpg by 2025 and 81mpg by 2030. Other low-hanging fruit, she said, is tackling heavy-duty truck emissions. She said that heavy-duty vehicles represent 10 percent of the global fleet but 50 percent of transportation emissions.

Dan Ryan, the director of Government and Public Affairs for Mazda North America, said that the auto company is concerned about emissions but unconvinced that betting early on EVs will pay off for the company and allow it to reinvest in new technology. Instead, Mazda has taken a more pragmatic approach with its efficiency-minded Skyactiv engines (Ars drove the Skyactiv-X, Mazda's breakthrough compression ignition engine, in January).

Ryan said that Mazda would eventually have cars with some level of electrification by 2019, but for now, the company is focused on making improvements "well-to-wheel," that is, from the oil well to the auto itself. (Mazda has argued that, taking into account the carbon-intense sources of electricity, its efficient engines are as polluting as EVs in some parts of the world). "What is our overall objective?" Ryan asked rhetorically. "Do we want to reduce overall greenhouse gas or do we just want to see more EVs on the road?"

Of course, as more and more utility-grade electricity becomes renewable or low-emission, that argument doesn't hold up as well. But until then, Mazda's pitch is more than a talking point. The automaker has the best average fleet economy of any manufacturer selling cars in the US (30.1mpg and 295g CO 2 /mile) even without having any hybrids or EVs in its lineup.

Although none of the panel members disputed that an electric future is coming, all of them believe that investing in more efficient ICE vehicles is critical to meeting climate change goals. "We think it’s important to not let the perfect be the enemy of the good," Ryan concluded.