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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




This study is as credible as all others. Too bad that 25 years (1980-2005) were wasted and even negative with regards to fleet efficiency improvement.

Many of those gas guzzlers, produced between 1980 and 2005, will be around for another 10+ years because more and more people cannot afford to buy newer more efficient vehicles.

Smaller more efficient ICE and 6, 7, 8 speed transmissions + the arrival of many more HEVs, PHEVs and BEVs could change the total fleet efficiency significantly, if we could afford to scrap our 1980/2005 dinosaurs.


It can't happen soon enough, I just heard there been ANOTHER oil rig explosion in the the Gulf;


Too bad some of you blind Cassandras don't recognize the tripling in fuel economy that has happened since 1973. Back then, when OPEC was beginning to exert its power, the US CAFE was 8-9 mpg. The very best car obtained 14 city and 16 highway. It was the venerable subcompact Bug.

Using exactly the same measuring stick scale it has long been 27.5 mpg. And the achieved CAFE for model year 2009, was 32.6 mpg using exactly that same CAFE yardstick. For the second year in a row the domestic automakers having a better composite CAFE figures than the imports.

So it has tripled or quadrupled from what it used to be. What car other than a super powered megabuck exotica, or a Suburban SUV obtains mileage as poor as 14/16 of the 42 HP VW Beetle?

We are on the verge of an enormous increase in fuel economy; and for the first time technology has advanced to the point that oil substitutes rather than simply squeezing a few more mpg is becoming possible. The Volt is a full family-sized auto, that will obtain 230 mpge city, and 100+ mpge highway with a triple digit combined.

That is roughly a quadrupling of the current 33 mpg CAFE, and double this supposed 2035 impossible target. It is very close to seeing HCCI semi-diesel engines that enjoy both the benefit of diesel mileage, with the half the weight and complexity of a gasoline ICE engine.

Meanwhile the American auto, unlike the rest of the world, has been transformed to a perfectly clean non toxic generator, producing cleaner air out of the tailpipe than going into the intake.


" Meanwhile the American auto, unlike the rest of the world, has been transformed to a perfectly clean non toxic generator, producing cleaner air out of the tailpipe than going into the intake. "

Are you going to pipe that "cleaner exhaust" back into the cabin of your car and prove that is true?


In 73 I was driving a Fiat that got 30 miles to the gallon.


There are lots of very economical cars available in Europe.

Here is a recent review of 14 of them (<100 gms CO2/km) by Auto express of the UK.

You won't pull a boat with any of these, but they will do 90% of what people need (or do what 90% of people need).

There is a boatload of innovation coming down the line (start/stop, various flavors of hybridization including hydraulic and improvements in ICE design), so I don't see what the problem is.

It would seem important to keep the pressure up with new CAFE rules or increased (or continued) taxation on fuel, to keep people focused on economy.


EXDEMO: Please have another look at the graph. Fleet efficiency went down for 25 years between 1980 and 2005. Somebody must be responsible.

Of course, deniers will maintain that it is government's and CAFE's fault but the majority is stating to know who did it and buying more and more imported more efficient vehicles and (selectively) the more efficient locally produced units.

We have been had for 25+ years. It is time to wake up.


Also, the graph is misleading, it should be a log graph on the Y axis.
Getting from 14 - 12 L/100Km was much easier than getting from 6 to 4 will be.

The years from 1985 - 2003 were characterized by cheap oil, so, in a "tax free" country, there was no incentive to reduce fuel consumption.


since 1973. Back then, when OPEC was beginning to exert its power, the US CAFE was 8-9 mpg. The very best car obtained 14 city and 16 highway. It was the venerable subcompact Bug.

That's funny I owned a 73 Beetle and got 30/35 mpg.


Even funnier is that my parents owned a 57 VW bus, and THAT got 28 mpg (23 mpg US).

Will S

I've been averaging 60+mpg for the last ten years (2000 Honda Insight), so nothing in this report even mildly surprises me. Given the number of 100+ mpg four passenger cars in the Progressive X-Prize automotive contest, this objective should be considered a breeze.

Stan/ExDemo said;

The very best car obtained 14 city and 16 highway. It was the venerable subcompact Bug.

?? Where do you get your information from??

Bosch L-Jetronic fuel injection boosted the Super Beetle's fuel economy from 25 to 33 mpg.

Henry Gibson

There is now no excuse for not making plug in hybrid cars. AC propulsion proved that they could be made 20 years ago with lead batteries. CalCars confirmed this five years ago. Getting electricity from the grid removes the polution from the city center and, in France and Norway removes it entirely. And people do not pay the oil speculators very much. Oil can be removed at a profit from the ground in most places where it is produced at less than 5 dollars a barrel. When the cost gets to 60 dollars a barrel you can start believing in an oil shortage in nature that is not caused by speculators. Also when the US and Australia build large numbers of coal to gasoline conversion factories you can believe in a natural shortage of oil. ..HG..


There is no valid reason why American auto builders are not producing 100+ mpg vehicles today.

They would weigh about 1000 pounds. The transmission would be Copper wires and a computer. The genset would consist of a Turbocharged diesel, two-cylinder opposed and air cooled, directly driving a generator.

The 92% efficient electric motors would have outer rotors driven by stationary Stators.

Volt has many of the requirements right but their execution has been terrible.


Turbo diesel hybrid, sounds like the 3 PNGV cars we had in 1999. Then the 3 U.S. automakers went back to building large SUVs because Junior was in the White House.


The PNGV programme should have delivered "production-ready" prototypes by 2004 according to the schedule. With Al Gore in the White House, you might have had those cars on the road by now.

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