New Technologies Can Result in Significant Fuel Savings for Passenger Vehicles, But at Higher Purchase Prices for Consumers

(National Acadamies) 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, says a new report by the National Research Council. The technologies would also increase vehicle purchase costs for consumers, sometimes by as much as several thousand dollars.

"Reducing the amount of fuel we use is an important goal for the nation and for the individual consumer," said Trevor O. Jones, chair of the committee that wrote the report and chair and CEO of ElectroSonics Medical Inc., Cleveland. "These technologies – whether adopted individually or in combination – offer the potential to meet that objective. Consumers will need to consider the trade-offs between higher vehicle prices and saving fuel and money at the gas pump."

The committee was not charged with determining how long it would take for money saved on fuel purchases to offset higher vehicle prices; this analysis will be conducted by regulatory agencies as they develop standards for light-duty vehicle fuel economy and greenhouse gas emissions.

Using a 2007 base vehicle, the committee estimated the potential fuel savings and costs to consumers of available technology combinations for three types of engines: spark-ignition gasoline, compression-ignition (CI) 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 committee's estimates are based on a variety of factors including recent reports from regulatory agencies and other sources, component cost estimates from suppliers, discussions with experts, and comparisons of prices and fuel consumption of similar vehicles. Estimated price increases are based on current economic conditions and the concept of "incremental retail price equivalent (RPE) cost," which represents the average additional price consumers would pay for a fuel economy technology.

The report 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, vehicle stickers should provide consumers with fuel consumption data in addition to fuel economy information, the report says.

Also, the National Highway Traffic and Safety Administration and the U.S. Environmental Protection Agency should review and revise fuel economy test procedures so they better reflect vehicle operating conditions and provide incentives to manufacturers to reduce fuel consumption. The report identifies an improved method that NHTSA and EPA should use to more accurately estimate a technology's ability to reduce fuel consumption.

Spark-ignition engines – which will continue to be the dominant type of engine in the U.S. for the next 10 to 15 years – have seen many technology improvements that are producing significant fuel savings. As a result, automobile manufacturers are able to create packages of technologies that can meet cost and effectiveness targets in small, incremental steps. For example, the report notes the promise of cylinder deactivation – which enables a six- or eight- cylinder engine to run on fewer cylinders when full-engine power is not needed, such as on flat roads. Deactivation can reduce fuel consumption by as much as 10 percent at a retail vehicle price increase of $350 to $500, the report says.

Engines that run on diesel fuel may become more popular in the United States now that new emission control technologies are allowing for a wide range of diesel engines to meet federal and state air quality standards, the report says. Replacing a 2007 model spark-ignition engine with a base-level CI diesel engine – including a six-speed dual clutch transmission and other efficiencies – could reduce fuel consumption by about 33 percent, and with an RPE of about $4,800 for a six-cylinder engine. Advanced CI diesel engines, expected to reach the market in the next five years, could reduce fuel consumption an additional 7 percent to 13 percent, with estimated vehicle RPE cost of about $4,600 for small passenger cars to $5,900 for intermediate or larger vehicles.

Hybrid vehicle technologies are one of the most active areas of research and development. The degree of hybridization can vary from minor vehicle stop-start systems to complete vehicle redesign. A fully hybrid vehicle could reduce fuel consumption by about 50 percent at an estimated price increase of up to $9,000 a vehicle depending on vehicle size. The report notes that a significant part of reducing fuel consumption in full hybrids results from complete vehicle redesign that incorporates low-rolling-resistance tires, improved aerodynamics, and smaller, more efficient spark-ignition engines.

Hybrid vehicle improvements in the next 10 to 15 years will occur primarily in reducing costs of hybrid power train components and improving battery performance. While many challenges remain in developing lithium-ion battery technology, small, limited-range battery electric vehicles will be on the market in the next decade, the committee predicted. However, fuel-cell vehicles will not represent a significant fraction of light-duty vehicles on the road in the next 15 years.

The report also examines a range of non-engine vehicle technologies. Relatively minor changes that do not involve re-engineering the vehicle or require recertification for fuel economy, emissions, or safety can be implemented within the next several years. They include reducing vehicle mass by using lighter materials, improving aerodynamics, or switching to low-rolling-resistance tires. Two important areas of research for long-range improvements include transmission systems and light-weighting – making vehicles very light with new materials under development.

The study was sponsored by the National Highway Traffic Safety Administration. The National Academy of Sciences, National Academy of Engineering, Institute of Medicine, and National Research Council make up the National Academies. They are private, nonprofit institutions that provide science, technology, and health policy advice under a congressional charter. The Research Council is the principal operating agency of the National Academy of Sciences and the National Academy of Engineering. READ MORE Order Study