With ethanol being widely available in fuel pumps everywhere, driving your car on empty may cause engine failure. Ethanol mixed with fuel (standard gas at most stations) can separate–phase separation–and the ethanol, which contains water, will sink to the bottom of the fuel tank. If you keep driving while the tank is almost empty, it could suck the ethanol and water mixture directly into the engine potentially resulting in failure and costly repairs. It the fuel tank is only one-fourth full, it is recommended to fill it up; thus avoiding this problem altogether.
The above was written by Kara Bishop and was published in the Fall 2012 edition of Vehicle MD.