Since it appears that this synthetic oil has the density of water at 15 deg C, use the conversions for water at this temperature. For other temperatures ask the makers.
To IFRs, with such a high degree of exactitude (five significant digits) one needs to add at what T/P is the water density taken, say 60oF/1 atm. abs.
Do you agree ?
Agreed. But only the one with water in it, which should be at STP. Cubic feet to gallons and liters is independant of temperature, pressure, gravity, etc.