Formula to convert 3.9 liters to gallons is to multiply 3.9 by 0.264172 (this is the value for 1 liter to gallon).
Convert 3.9 Liters to Gallons results
3.9 x 0.264172052 = 1.03027100436
3.9 l = 1.03 gal
To conclude the answer for 3.9 liters is one point zero three gallons