The formula with 16 substituted
litres = 16 × 3.785411784 = 60.567
The constant is an exact definition, not a rounded factor: the mile is 1.609344 km, the US gallon is 3.785411784 litres and the imperial gallon is 4.54609 litres. The Gallons to Litres Converter explains where each comes from and gives a longer table.
16 US gallons is 60.567 litres. 16 imperial gallons, the gallon behind British mpg figures, is 72.737 litres.
What 16 US gallons means in practice
16 US gallons is 60.567 litres and 16 imperial gallons is 72.737 litres. Sixteen US gallons is a typical tank for a mid-size SUV, and about what a 60 litre European tank holds, which is the same class of vehicle described in two units.