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A Fuel Economy Measurement Dilemma - Certification Testing vs. Customer Driving
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English
Abstract
Many factors can be cited which produce differences between the fuel economy values obtained during the exhaust emission certification process and the economy experienced by car owners. Admittedly, all laboratory tests are compromised by many assumptions, approximations, and practical test limitations. The main value of the EPA test procedure is that it has provided a uniform test method for all manufacturers which produces vast amounts of comparative fuel economy information. Changes to the procedure to make it more “representative” have reduced its usefulness for comparisons to previous years.
The concept of labeling cars with a “representative” fuel economy value is certain to result in some customer misinformation and dissatisfaction. At best, current labeling methods can be expected to indicate real vehicle differences only when label values differ by more than 2 mi/gal (0.85 km/l). Furthermore, wide variations in customer fuel economy (ranging up to 15 mi/gal) for the same EPA label value are bound to make some people regard the label values as misleading.
Changes in new car fuel economy have a significant impact upon future fuel demand projections. A stable fuel economy measurement procedure and an understanding of the factors which relate certification to average customer economy are needed to reduce the uncertainties in such a projection.
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Citation
Marks, C., "A Fuel Economy Measurement Dilemma - Certification Testing vs. Customer Driving," SAE Technical Paper 780938, 1978, https://doi.org/10.4271/780938.Also In
References
- Environmental Protection Agency “Fuel Economy of Motor Vehicles” Federal Register Doc. 78 4126 43 33 February 16 1978
- McNutt Barry D. Pirkey Diane Dulla Robert Miller Craig “A Comparison of Fuel Economy Results from EPA Tests and Actual In-Use Experience, 1974-1977 Model Year Cars.” Paper 780037 presented at SAE Congress Detroit, Michigan February 1978
- Austin T. C. Michael R. B. Service G. R. “Passenger Car Fuel Economy Trends Through 1976.” Paper 750957 presented at SAE Automobile Engineering Meeting Detroit, Michigan October 1975
- Code of Federal Regulations Office of the Federal Register
- Kruse Ronald E. Huls Thomas A. “Development of the Federal Urban Driving Schedule.” Paper 730553 presented at SAE Automobile Engineering Meeting Detroit, Michigan May 1973
- Austin Thomas C. Hellman Karl H. Don Paulsell C. “Passenger Car Fuel Economy During Non-Urban Driving.” Paper 740592 presented at SAE West Coast Meeting Anaheim, California August 1974
- Austin Thomas C. Hellman Karl H. “Passenger Car Fuel Economy as Influenced by Trip Length.” Paper 750004 presented at SAE Congress Detroit, Michigan February 1975
- U.S. Environmental Protection Agency “Determination and Use of Alternative Power Absorber Settings.” February 8 1978
- Conference Proceedings “Tire Rolling Losses and Fuel Economy - An R and D Planning Workshop.” SAE Highway Tire Committee Cambridge, Massachusetts October 1977
- U.S. Federal Highway Adminstration “Highway Statistics”