Formula to convert 15.9 liters to gallons is to multiply 15.9 by 0.264172 (this is the value for 1 liter to gallon).
Convert 15.9 Liters to Gallons results
15.9 x 0.264172052 = 4.20033563316
15.9 l = 4.2 gal
To conclude the answer for 15.9 liters is four point two gallons