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Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.


The impacts of fuel consumption by light-duty vehicles are profound, influencing economic prosperity, national security, and Earth’s environment. Increasing energy efficiency has been a continuing and central objective for automobile manufacturers and regulators pursuing objectives that range from reducing vehicle operating costs and improving performance to reducing dependence on petroleum and limiting greenhouse gas emissions. Given heightened concerns about the dangers of global climate change, the needs for energy security, and the volatility of world oil prices, attention has again been focused on reducing the fuel consumption of light-duty vehicles. A wide array of technologies and approaches exist for reducing fuel consumption. These improvements range from relatively minor changes with low costs and small fuel consumption benefits—such as use of new lubricants and tires—to large changes in propulsion systems and vehicle platforms that have high costs and large fuel consumption benefits.


The rapid rise in gasoline and diesel fuel prices experienced during 2006-2008 and growing recognition of climate-change issues have helped make vehicle fuel economy an important policy issue once again. These conditions have motivated several recent legislative and regulatory initiatives. The first major initiative was the mandate for increased CAFE standards under the Energy Independence and Security Act of 2007. This legislation requires the National Highway Traffic Safety Administration (NHTSA) to raise vehicle fuel economy standards, starting with model year 2011, until they achieve a combined average fuel economy of at least 35 miles per gallon (mpg) for model year 2020. The policy landscape has also been significantly altered by separate Supreme Court decisions related to the regulation of carbon dioxide as an air pollutant and the California greenhouse gas vehicle standards. These decisions helped spur the Obama administration to direct the U.S. Environmental Protection Agency (EPA) and the NHTSA to develop a joint fuel economy/greenhouse gas emission standard for light-duty vehicles that mirrors the stringency of the California emissions standard. Finalized on April 1, 2010, the rule requires that fleet-averaged fuel economy reach an equivalent of 35.4 mpg by model year 2016.

The significant downturn in the United States and world economies that occurred during the course of this study has had substantial negative impacts on the global automobile industry. Most manufacturers have experienced reduced sales and suffered losses. The automobile industry is capital intensive and has a very steep curve on profits around the break-even point: a small increase in sales beyond the break-even point can results in large profits, while a small decrease can result in large losses. Consumer spending decreased markedly due to lack of confidence in the economy as well as difficulties in the credit markets that typically finance a large portion of vehicle purchases. The U.S. market for light-duty vehicles decreased from about 16 million vehicles annually for the last few years to about 10 million in 2009. The overall economic conditions resulted in Chrysler and GM deciding to file for Chapter 19 bankruptcy and in Ford excessively leveraging its assets. GM and Chrysler have recently exited bankruptcy, and the U.S. government is now the major shareholder of GM. Fiat Automobiles has become a 20 percent shareholder in Chrysler, with the potential to expand its ownership to 35 percent, and the newly formed Voluntary Employee Beneficiary Association has a 55 percent stake.

These economic conditions will impact automotive companies’ and suppliers’ ability to fund in a timely manner the R&D necessary for fuel economy improvements and the capital expenditures required. Although addressing the impact of such conditions on the adoption of vehicle fuel economy technologies is not within the purview of this committee, these conditions do provide an important context for this study. Manufacturers will choose fuel economy technologies based on what they think will be most effective and best received by consumers. Customers also will have a central role in what technologies are actually chosen and will make those choices based partly on initial and operating costs.

Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.

Subsidies and other incentives also can significantly impact the market acceptance rate of technologies that reduce fuel consumption. Finally, adoption of these technologies must play out in a sometimes unpredictable marketplace and policy setting, with changing standards for emissions and fuel economy, government incentives, consumer preferences, and other events impacting their adoption. Thus, the committee acknowledges that technologies downplayed here may play a bigger role than anticipated, or that technologies covered in this report may never emerge in the marketplace.

The timing for introducing new fuel consumption technologies may have a large influence on cost and risk. The individual vehicle models produced by automobile manufacturers pass through a product cycle that includes introduction, minor refreshments of design and features, and then full changes in body designs and power trains. To reduce costs and quality concerns, changes to reduce fuel consumption normally are timed for implementation in accordance with this process. Further, new technologies are often applied first in lower-volume, higher-end vehicles because such vehicles are better able to absorb the higher costs, and their lower volumes reduce exposure to risk. In general, 2 to 3 years is considered the quickest time frame for bringing a new vehicle model to market or for modifying an existing model. Significant carryover technology and engineering from other models or previous vehicle models are usually required to launch a new model this quickly, and the ability to significantly influence fuel consumption is thus smaller. More substantial changes to a model occur over longer periods of time. Newly styled, engineered, and redesigned vehicles can take from 4 to 8 years to produce, each with an increasing amount of new content. Further, the engine development process often follows a path separate from that for other parts of a vehicle. Engines have longer product lives, require greater capital investment, and are not as critical to the consumer in differentiating one vehicle from another as are other aspects of a car. The normal power train development process evolves over closer to a 15-year cycle, although refinements and new technologies will be implemented throughout this period. It should be noted that there are significant differences among manufacturers in their approaches to introducing new models and, due to regulatory and market pressures, product cycles have tended to become shorter over time.

Although it is not a focus of this study, the global setting for the adoption of these fuel economy technologies is critical. The two main types of internal combustion engines, gasoline spark-ignition (SI) and diesel compression-ignition (CI), are not necessarily fully interchangeable. Crude oil (which varies in composition) contains heavier fractions that go into diesel production and lighter fractions that go into gasoline. A large consumer of diesel, Europe diverts the remaining gasoline fraction to the United States or elsewhere. China is now using mostly gasoline, and so there is more diesel available globally. And automobile manufacturers and suppliers worldwide are improving their capabilities in hybrid-electric technologies. Further, policy incentives may help favor one technology over another in individual countries.


The NHTSA has a mandate to keep up-to-date on the potential for technological improvements as it moves into planned vehicular regulatory activities. It was as part of its technology assessment that the NHTSA asked the National Academies to update the 2002 National Research Council report Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards (NRC, 2002) and add to its assessment other technologies that have emerged since that report was prepared. The statement of task (see Appendix B) directed the Committee on the Assessment of Technologies for Improving Light-Duty Vehicle Fuel Economy to estimate the efficacy, timing, cost, and applicability of technologies that might be used over the next 15 years. The list of technologies includes diesel and hybrid electric power trains, which were not considered in the 2002 NRC report. Weight and power reductions also were to be included, but not size or power-to-weight ratio reductions. Updating the fuel economy-cost relationships for various technologies and different vehicle size classes as represented in Chapter 3 of the 2002 report was central to the study request.

The current study focuses on technology and does not consider CAFE issues related to safety, economic effects on industry, or the structure of fuel economy standards; those issues were addressed in the 2002 report. The new study looks at lowering fuel consumption by reducing power requirements through such measures as reduced vehicle weight, lower tire rolling resistance, or improved vehicle aero dynamics and accessories; by reducing the amount of fuel needed to produce the required power through improved engine and transmission technologies; by recovering some of the exhaust thermal energy with turbochargers and other technologies; and by improving engine performance and recovering energy through regenerative braking in hybrid vehicles. Additionally, the committee was charged with assessing how ongoing changes to manufacturers’ refresh and redesign cycles for vehicle models affect the incorporation of new fuel economy technologies. The current study builds on information presented in the committee’s previously released interim report (NRC, 2008).


The committee organized its final report according to broad topics related to the categories of technologies important for reducing fuel consumption, the costs and issues associated with estimating the costs and price impacts of these technologies, and approaches to estimating the fuel consumption benefits possible with combinations of these tech-

Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.

nologies. Chapter 2 describes fundamentals of determining vehicle fuel consumption, tests for regulating fuel economy, and basic energy balance concepts, and it discusses why this report presents primarily fuel consumption data. Chapter 3 describes cost estimation for vehicle technologies, including methods for estimating the costs of a new technology and issues related to translating those costs into impacts on the retail price of a vehicle. Chapters 4 through 7 describe technologies for improving fuel consumption in spark-ignition gasoline engines (Chapter 4), compression-ignition diesel engines (Chapter 5), and hybrid-electric vehicles (Chapter 6). Chapter 7 covers non-engine technologies for reducing light-duty vehicle fuel consumption. Chapter 8 provides a basic overview of and discusses the attributes of two different approaches for estimating fuel consumption benefits—the discrete approximation and the full-system simulation modeling approaches. Chapter 9 provides an estimate of the costs and the fuel consumption benefits of multiple technologies for an array of vehicle classes. The appendixes provide information related to conducting the study (Appendixes A through C), a list of the acronyms used in the report (Appendix D), and additional information supplementing the individual chapters (Appendixes E through K).


NRC (National Research Council). 2002. Effectiveness and Impact of Corporate Average Fuel Economy (CAFE) Standards. Washington, D.C.: National Academy Press.

NRC. 2008. Interim Report of the Committee on the Assessment of Technologies for Improving Light-Duty Vehicle Fuel Economy. Washington, D.C.: The National Academies Press.

Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
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Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
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Suggested Citation:"1 Introduction." National Research Council. 2011. Assessment of Fuel Economy Technologies for Light-Duty Vehicles. Washington, DC: The National Academies Press. doi: 10.17226/12924.
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Various combinations of commercially available technologies could greatly reduce fuel consumption in passenger cars, sport-utility vehicles, minivans, and other light-duty vehicles without compromising vehicle performance or safety. Assessment of Technologies for Improving Light Duty Vehicle Fuel Economy estimates the potential fuel savings and costs to consumers of available technology combinations for three types of engines: spark-ignition gasoline, compression-ignition diesel, and hybrid.

According to its estimates, adopting the full combination of improved technologies in medium and large cars and pickup trucks with spark-ignition engines could reduce fuel consumption by 29 percent at an additional cost of $2,200 to the consumer. Replacing spark-ignition engines with diesel engines and components would yield fuel savings of about 37 percent at an added cost of approximately $5,900 per vehicle, and replacing spark-ignition engines with hybrid engines and components would reduce fuel consumption by 43 percent at an increase of $6,000 per vehicle.

The book focuses on fuel consumption—the amount of fuel consumed in a given driving distance—because energy savings are directly related to the amount of fuel used. In contrast, fuel economy measures how far a vehicle will travel with a gallon of fuel. Because fuel consumption data indicate money saved on fuel purchases and reductions in carbon dioxide emissions, the book finds that vehicle stickers should provide consumers with fuel consumption data in addition to fuel economy information.


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