Washington, D.C. – Various combinations of commercially-available technologies could greatly reduce fuel consumption without compromising vehicle performance or safety, but would increase the purchase price by as much as several thousand dollars, according to a new report by the U.S. National Research Council (NRC).

“Reducing the amount of fuel we use is an important goal for the nation and for the individual consumer,” said Trevor Jones, chair of the committee producing the report. “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.”

Using a 2007 base vehicle, the committee estimated the potential fuel savings and cost to consumers of available technology combinations for spark-ignition (gasoline) engines, compression-ignition diesels, and hybrids. According to 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 per cent, with an additional cost of US$2,200 to the consumer.

Replacing spark-ignition engines with diesel engines and components would yield fuel savings of about 37 per cent at an added cost of approximately $5,900 per vehicle, while replacing them with hybrid engines and components would reduce fuel consumption by 43 per cent, and increase costs by $6,000.

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, while fuel economy measures how far a vehicle will travel with a gallon of fuel. The report recommends that vehicle stickers should include both fuel economy and fuel consumption data, because fuel consumption data indicate money saved on fuel purchases and reductions in carbon dioxide emissions.

Spark ignition engines, which will continue to be the dominant type of engine in the U.S. for the next ten 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, such as cylinder deactivation, which can reduce fuel consumption by as much as 10 per cent, with a retail vehicle increase of $350 to $500.

Diesel engines are becoming more popular in the U.S., and replacing a 2007 model spark-ignition engine with a base-level diesel, including a six-speed dual-clutch transmission and other efficiencies, could reduce fuel consumption by about 33 per cent, with a cost of about $4,800 for a six-cylinder engine. Advanced diesel engines, expected to reach the market in the next five years, could reduce consumption by an additional seven to 13 per cent, with an estimated cost of $4,600 for small cars, to $5,900 for larger or intermediate vehicles.

Hybrid design can vary from minor vehicle stop-start systems to complete vehicle redesign. A fully hybrid vehicle could reduce fuel consumption by about 50 per cent, with an estimated price increase of up to $9,000. 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 engines.

Hybrid improvements in the next ten to 15 years will occur primarily in reducing the costs of components and improving battery performance. Fuel cell vehicles will not represent a significant fraction of light-duty vehicles on the road in the next 15 years.

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