The following are possible reasons why motorists might see variations in vehicle tank capacity indications as reported by the National Institute of Standards and Technology.
Vehicle tank capacity rating is only an approximate volume and may vary by as much as 3% from actual tank capacity as a result of normal variations in design characteristics.
Typically the owner’s manual provides a reasonable estimate of the vehicles fuel tank capacity. The tank capacity’s numerical value is reported in tenths of whole figures rounded to the nearest value therefore represents an approximate volume.
Attempts by drivers to fill the tank beyond the pumps automatic shut-off point can result in fuel being drawn into the pump’s or the vehicle’s vapor recovery systems. The vehicle’s fuel tank capacity does not include the vapor headspace (that portion of the tank compartment at a level above the filler pipe neck) or the volume of the filler pipe. Sometimes drivers ignore the pump nozzles’s automatic shut-off and continue to hold the nozzle operating lever open in an attempt to deliver additional fuel. When this happens the additional fuel begins to fill the vapor headspace and the filler pipe that are not considered part of the tanks rated capacity, thus resulting in a delivery of fuel greater than the fuel tank capacity rating stated in the owners manual.
Another scenario that can prompt consumer complaints involves the fuel tank capacity and the fuel gauge indication. When the fuel gauge indicates a particular level, the customer frequently assumes that this represents a corresponding fraction of the fuel tank capacity. For example, on a fuel tank with an 18 gallon rating in the owners’ manual, the consumer assumes that a “half-full” fuel gauge indication means that 9 gallons of fuel remains in the tank. When the consumer is able to dispense more than 9 gallons of fuel into that “half-full” tank, the consumer assumes that there is a total of more than 18 gallons of fuel in the tank, thus exceeding the fuel tank rating listed in the owner’s manual. The consumer than concludes that the gasoline dispenser must be in error.
If you have any questions about this information, please contact the Greene County Department of Weights and Measures at (518)731-2257.
David Stockman – Director of Weights and Measures, is a member of the Northeast Weights and Measures Association and works closely with New York State Department of Agriculture and Markets, Division of Weights and Measures located in Albany.