WATER TOLERANCE OF GASOLINE-ALCOHOL BLENDS: D6422
EXPLANATION
Gasoline-alcohol blends have a very limited ability to retain water in solution or in a stable suspension, and if the amount of water in the blend exceeds this limit, the fuel will separate into a lower aqueous and an upper hydrocarbon phase. Temperature is the critical factor governing the ability of a fuel to retain water without separating. This test method determines the maximum temperature at which the fuel will separate. This test method is applicable to gasoline-alcohol blends for use as fuels in spark-ignition engines that contain saturated C1 to C4 alcohols only. This test method does not apply to fuels that contain an alcohol as the primary component, such as M85 or E85, or to gasoline-ether blends.
TEST SUMMARY
A fuel sample is cooled at a controlled rate to its lowest expected storage or use temperature and is periodically observed for phase separation. The apparatus of Test Method D2500 or a dry ice-isopropyl alcohol bath may be used. A maximum cooling rate of 2 ° C/min is specified because phase separation in gasoline-alcohol blends can have a relatively long but unpredictable induction period.
TEST PRECISION
The precision and bias of this test method are currently being determined.
