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Study Finds That Tripling US LDV New Fleet Fuel Efficiency by 2035 Through Evolutionary Change is Ambitious But Doable

New fleet efficiency horizon in terms of energy intensity and fuel consumption rate compared to historical fleet averages and recent US regulations. Source: DeCicco 2010. Click to enlarge.

Tripling US new light-duty vehicle fleet fuel efficiency by 2035 through evolutionary change—e.g., relying heavily on improvements in advanced engines and in the application of hybrid drive technology—rather than on revolutionary alternatives such as plug-in vehicles or hydrogen requiring extensive new infrastructure is an “ambitious but defensible horizonaccording to a new study by John DeCicco, a senior lecturer at the University of Michigan’s School of Natural Resources and Environment and faculty fellow.

DeCicco’s analysis shows that optimizing internal combustion engines plus rising adoption of grid-free hybrids will enable new fleet fuel economy (unadjusted) to reach 52 mpg (4.52 L/100km) by 2025 and 74 mpg (3.18 L/100km) by 2035. Adjusted on-road fuel economy correspondingly would be 41 mpg (5.74 L/100km) and 60 mpg (3.92 L/100km). CO2 emissions, with AC, would reach 104 g/mi in 2035. The study, “A Fuel Efficiency Horizon for US Automobiles”, was prepared for The Energy Foundation.

Reaching [this horizon] will entail rising costs that are best seen as opportunity costs for features that might otherwise appear in cars if high fuel efficiency levels are not sought. Achieving this horizon at the costs projected means foregoing further gains in average acceleration performance, a marked departure from past trends. If instead performance rises in line with its historical trend, the 2035 horizon drops from tripled down to roughly doubled fuel efficiency. Nevertheless, improving the fleet toward such a horizon through evolutionary change remains less costly than “revolutionary” alternatives requiring extensive new infrastructure. In short, attaining or even approaching the fuel efficiency horizon projected here will yield substantial benefits for reducing oil consumption and limiting GHG emissions from the transportation sector.

—A Fuel Efficiency Horizon for US Automobiles

The study examines how far automobile efficiency can be taken if it is pursued with determination, using an analysis that assumes success in technology and design strategies that offer “revolution by evolution.” The study does not perform new detailed engineering analysis, but rather synthesizes published results under an assumption that efficiency gains from evolutionary technology changes are maximized on a fleetwide basis.

Many analyses highlight alternative technologies for replacing internal combustion engines and petroleum-based fuels, such as grid-based vehicle electrification, biofuels, hydrogen or natural gas. Others point to radical changes in vehicle materials and design. Proponents of these options marshal technological optimism in scenarios that show how their alternatives will revolutionize the automobile. While such options mature, it will be crucial to pursue evolutionary advances in existing systems, which can be greatly improved at cost, but at much less cost and with none of the other barriers faced by alternative technologies.

—A Fuel Efficiency Horizon for US Automobiles

DeCicco says that the rate of technology progress, particularly for the degree of hybridization likely to be needed, he assumes are in line with those of some major automotive technology changes in the past; the challenge is cost, which rises steadily as greater use of advanced technology is required.

Nevertheless, projected fuel savings greatly exceed upfront costs and this evolutionary horizon remains less costly than revolutionary changes in vehicles based on electric grid connection, hydrogen or other alternatives that entail extensive new infrastructure. As interpreted here, however, these options are used only as an existence proof of the potential for high fuel efficiency rather than as a literal technology pathway to be implemented. Thus, the view is technologically agnostic and reflects opportunities identified through engineering fundamentals.

—A Fuel Efficiency Horizon for US Automobiles

To entice buyers away from a focus on power, and toward smart technology, DeCicco identifies emerging trends for what he dubs efficiency compatible design strategies. Amenities like Bluetooth hookups, communication bandwidth and other information technology enhance customer value with minimal demands on power.

Compatible strategies are approaches for both individual vehicles and product plans that enhance customer value by emphasizing features that are not inherently fuel consumptive. Such options include intelligent systems content, matching performance to real world driving needs, creative downsizing, interior packaging and styling—in short, appealing to consumers in ways that are in line with, as opposed to work against, fuel efficiency.

—A Fuel Efficiency Horizon for US Automobiles

The report develops new interpretations of technology cost estimates that better depict the benefits of ongoing innovation while acknowledging the limits of how much consumers can spend. The analysis reflects the three-way trade-off among efficiency, performance and cost that the car market is likely to face in the years ahead.

The fleet I’ve modeled for 2025 does not give up any of the performance and creature comforts consumers already enjoy. You don’t have to go back to being Fred Flintstone, but you will see lower fuel costs instead of ever more mass and muscle.

—John DeCicco



fred schumacher

A topic that has not been sufficiently discussed is the impact of automotive morphology.

We make excellent multi-purpose vehicles. What we don't make are single-purpose vehicles to satisfy 80% of private automotive useage: single occupant commuting.

A narrow, two-seat, three-wheel commuter weighing under 1,000 pounds could achieve 100 mpg efficiency. Without the need for exotic technology, such a vehicle could be produced for half the cost of a standard sedan.

In this post financial crash, Great Recession world, cost will be a major consideration for new vehicle purchase, more important than it was in the past. Americans won't switch to high efficiency vehicles if the cost is too high. Keep it under $10,000 and the transition will be fast. If it's over $30,000, the transition will slow to a crawl.


David D,

We do that everyday where I live. Phoenix is also an Air Complince area, like most of America, and unlike LA. But the tail pipe emissions of the new cars with modern engines and control, spew cleaner air from the tailpipe than goes into the intake.

You could think of it if you wish, that the government is requirinfg everyone tp purchaase "mobile air purifiers" and take them with, when ever they go someplace.

And yes I breathe that air, as you do. But you brain has been laundered sufficently, to not recognize that reality.

It has been a hard fight and effort to get that far to cleanse our air, and taken almost forty years; but that is where we are, with gasoline Otto cycle ICES, but not Diesels, yet.


Too bad that 25 years (1980-2005) were wasted and even negative with regards to fleet efficiency improvement.

The fleet improvement ended exactly with the beginning of Ronnie Raygun.

Clinton/Gore were either naive or stupid to think that Detroit would deliver on the promise of PNGV.


PNGV was to show that it could be done. The government can not force the U.S. automakers to build them. Toyota and Honda were apparently "naive and stupid" enough to actually build hybrids, the rest is history.

Roger Pham

"Clinton/Gore were either naive or stupid to think that Detroit would deliver on the promise of PNGV."

Detroit has delivered a lot throughout the years: from carbureted and dirty-exhaust gas-guzzling death traps of yesteryears without seat-belt nor air bag... to the modern ultra efficient, ultra-clean exhaust, very comfortable and very safe vehicles...all due to mandates from Washington D.C.

Detroit will deliver on the promise of PNGV if everyone will be told that the gov. will guarantee a steady rise in the prices of fuels years after years, may doubling the retail prices of fossil fuels after every 10 years or so. This will give everyone to prepare and shop for fuel-efficiency instead for large size, comfort or luxury. Most people will gladly pay 50%-100% more than the price of a basic vehicles to get extra features and vanities. Ergo, most people can more than afford the extra prices of full HEV (PNGV) if gasoline prices is high enough. When mass-produced over a number of years, the price premium of full HEV will come closer and closer to that of comparable non-hybrid.


That is a very good point Roger. Combine 50 mpg mandate with a 10% per year increase in the national gasoline tax. When people figure out that gasoline will cost $6-7 per gallon or more by 2020, they will find the most efficient vehicle that suits their purpose.

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