Epa Fuel Efficiency: Can It Be Improved?

The Environmental Protection Agency (EPA) is responsible for defining the methods used to calculate the fuel economy estimates that are posted on the window stickers of new cars and light trucks in the US. The EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL) tests new cars and trucks to ensure they comply with federal emissions and fuel economy standards. The EPA periodically updates its methodology to account for changes in vehicle technologies, driver behavior, and driving conditions. For example, in 2012, the EPA and the National Highway Traffic Safety Administration (NHTSA) unveiled a dramatic overhaul of vehicle fuel economy labels, providing car buyers with more information than ever before, including fuel economy, fuel costs, and environmental impacts.

EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL)

The National Vehicle and Fuel Emissions Laboratory (NVFEL) is a state-of-the-art facility located in Ann Arbor, Michigan, that plays a crucial role in the Office of Transportation and Air Quality (OTAQ). The NVFEL is dedicated to reducing air pollution from transportation sources, protecting both the environment and public health.

The laboratory is equipped with specialized equipment and staffed by highly trained professionals with diverse expertise, including engineering, chemistry, toxicology, law, and economics. The staff at NVFEL conduct comprehensive testing and research on a wide range of vehicles, engines, and fuels to ensure compliance with federal emissions and fuel economy standards. This includes testing new and used cars, light trucks, and heavy-duty engines throughout their useful lifetimes.

One of the key functions of the NVFEL is to develop and implement accurate test methods for measuring emissions. They also assess promising emissions reduction technologies, working to design and fabricate cost-effective solutions to reduce vehicle and engine emissions and improve fuel efficiency. The laboratory holds over 60 patents on advanced technologies, reflecting its commitment to innovation.

The NVFEL is also committed to sustainability and has implemented several measures to reduce its environmental impact. For example, they have upgraded their energy infrastructure, optimized cooling tower operations, and installed more efficient lighting fixtures, resulting in significant energy and water savings. The facility is ISO 14001:2015 certified, recognizing its environmental stewardship and commitment to the health and safety of its employees and visitors.

The Corporate Average Fuel Economy (CAFE) program

The CAFE standards are set at the "maximum feasible level", taking into account technological feasibility, economic practicality, the effect of other standards on fuel economy, and the need to conserve energy. The NHTSA sets separate standards for passenger cars and light trucks, with the goal of reducing fuel consumption, creating domestic jobs, and addressing global warming.

The CAFE standards define the fuel economy levels that manufacturers' fleets are required to meet in a given model year. If a manufacturer's average fuel economy falls below the standard, they must either apply CAFE credits or pay a penalty. The penalty is currently $14 per 0.1 mpg under the standard, multiplied by the manufacturer's total production for the US domestic market.

The CAFE program has undergone several revisions since its inception, with the most recent updates being proposed in 2023 for model years 2027-2031 for light-duty vehicles and 2030-2035 for heavy-duty trucks and vans. The proposed standards aim for an industry-wide fleet average of approximately 50.4 miles per gallon (mpg) for passenger cars and light trucks by 2031, and an average of roughly 2.851 gallons per 100 miles for heavy-duty pickup trucks and vans by 2035.

The CAFE program has had a significant impact on fuel consumption and emissions. According to a report by the National Academy of Sciences, in the absence of CAFE, motor vehicle fuel consumption in 2002 would have been approximately 14% higher. However, the standards have also been associated with increased vehicle costs and a potential increase in traffic fatalities due to the prevalence of smaller, lighter vehicles.

The effectiveness of the CAFE program has been a subject of debate, with some critics arguing that economic forces and consumer demand for more fuel-efficient vehicles are more influential in improving fuel economy than regulatory standards. Nonetheless, the CAFE program remains a key component of the United States' efforts to reduce fuel consumption, promote the development of more efficient vehicles, and address environmental concerns related to global warming and air pollution.

Gas Guzzler taxes

Gas Guzzler Tax is a provision established by the US Congress in the Energy Tax Act of 1978. The tax is levied on new cars that do not meet the required fuel economy levels. The tax was introduced to discourage the production and purchase of fuel-inefficient vehicles, and to incentivise the development and purchase of more fuel-efficient cars. The tax is only applied to passenger cars, and certain vehicle types like trucks, minivans, and SUVs are exempt. The Internal Revenue Service (IRS) is responsible for collecting the taxes from car manufacturers or importers, and the amount of tax is displayed on the window stickers of new cars. The tax rate increases as the fuel economy of the vehicle decreases, with the current rate ranging from $1,000 for vehicles with a fuel economy rating between 21.5 and 22.5 mpg, up to $7,700 for cars with a rating of 12.5 mpg or less.

The effectiveness of the Gas Guzzler Tax in improving overall fuel economy is questionable. While it has been in place for several decades, there are significant loopholes, and the current tax rates have not kept up with inflation, reducing their impact over time. Additionally, the improvement in fuel economy since the tax was introduced is likely due to separate regulations, such as the Corporate Average Fuel Economy standards, which impose fines directly on automakers.

Despite its limitations, the Gas Guzzler Tax has had some impact on the automotive industry. Many automakers have shifted their focus away from developing cars towards more fuel-efficient options like SUVs and pickups. However, certain exotic sports cars, sports sedans, and large luxury cars still carry the tax, with examples including the Bugatti Chiron, Cadillac CT5-V Blackwing, and the Rolls-Royce Phantom.

Fuel economy data for light-duty vehicles

The fuel efficiency figures for light-duty vehicles represent the sales-weighted harmonic average of the combined passenger car and light truck fuel economies. The average fuel efficiency of light-duty vehicles in the US can be calculated using the reciprocal of the sales-weighted average of gallons per mile, also known as the harmonic average.

From 1980 to 1994, the fuel efficiency data for light-duty vehicles, specifically those with a short wheelbase, included motorcycles. The data from 2007 onwards is calculated using a new methodology and is categorised differently. The new 'Light duty vehicle, short wheel base' category encompasses passenger cars, light trucks, vans, and SUVs with a wheelbase of 121 inches or less. The 'Light duty vehicle, long wheel base' category includes larger vehicles, such as large passenger cars, vans, pickup trucks, and SUVs with wheelbases larger than 121 inches.

Fuel efficiency in light-duty vehicles has seen an overall increase since 2004, largely due to the implementation of Corporate Average Fuel Economy (CAFE) standards. However, there was a decline in fuel efficiency from the late 1980s through the mid-2000s, which can be attributed to the rising popularity of light-duty trucks compared to passenger vehicles.

Horsepower in light-duty vehicles has generally increased from 1980 onwards, except for a dip in 2009 and 2010, likely due to the economic recession that reduced the production of larger vehicles such as SUVs and trucks.

Fuel economy and EV range testing

The US Environmental Protection Agency (EPA) is responsible for testing the fuel economy of new cars and trucks sold in the US to ensure they comply with federal emissions and fuel economy standards. The EPA's National Vehicle and Fuel Emissions Laboratory (NVFEL) conducts tests on vehicles by running them through a series of driving routines, also called cycles or schedules, that specify vehicle speed for each point in time during the laboratory tests.

The EPA confirms approximately 15% of all test results, but it is the manufacturers that are responsible for providing the fuel economy data used for labelling. Automakers are required to follow very specific test procedures and submit fuel economy data to the EPA for all their models each year. In general, vehicles are tested over five defined test cycles that were created to represent typical driving conditions in the US:

• City test: no heating, ventilation, or air conditioning (HVAC) operation
• Highway test: no HVAC operation
• More aggressive/high-speed test: no HVAC operation
• Hot test at 95°F: HVAC set to cool the cabin
• Cold test at 20°F: HVAC set to specific settings for heat and defrost

The results of these tests are then combined and weighted to estimate average use, which results in official miles per gallon (MPG) values. For plug-in electric vehicles (PEVs), the MPG equivalent (MPGe) conveys the energy consumption in terms of how many miles the vehicle could go on an amount of fuel with the same energy content as a gallon of gasoline.

For electric vehicles (EVs), vehicle testing provides important label information, such as fuel economy and range. The testing procedure involves driving a vehicle with a fully charged battery continuously over the EPA city cycle until the battery is depleted. This is repeated over the EPA highway cycle, and the distance driven is recorded for both cycles. Automakers also have the option of conducting a multi-cycle test, which consists of four city cycles, two highway cycles, and two constant speed cycles.

All testing is done in a laboratory on a dynamometer, and the results are adjusted to account for real-world factors that are not represented in the laboratory test procedures, such as the impact of air conditioning, cold temperatures, and aggressive driving behaviour.

Frequently asked questions