For this case we must perform a conversion of gallons to liters.
By definition, we have to:
1 gallon equals 3,78541 liters. By making a rule of three we have:
1 ----------------> 3.78541
12.8 -----------> x
Where "x" represents the amount of liters equivalent to 12.8 gallons.

Thus, 12.8 gallons of gasoline equals 48.453248 liters.
Rounding, we have: 48.45 liters
ANswer:
48.45 liters