The purpose of measuring the new-tank fueling emission was to determine the extent of the assembly-line fueling emission. It was predicted that the hydrocarbon emission rate would be very small since a new tank contains only air. The test results showed, however, that when fueled in the normal manner the new-tank emission rate was greater than that of a used tank. Only by fueling in a splash-free manner was the new-tank emission rate less than that of a used or in-service tank. Splash-free fueling showed no advantage, however, when applied to a used tank except when the dispensed fuel quantity was small.
The main cause for the new-tank emission rate exceeding that of the used tank was the degree and location of fuel splashing within the tank. A secondary cause was the larger volume of gas displaced from a new tank due to the establishment of a higher internal vapor pressure.