Example:
15 Gm/L = 35282187.494213 mile per US gallon
1 Gm/L = 2352145.832948 mile per US gallon | 1 mile per US gallon = 4.251437e-7 Gm/L
Conversion Steps:
15 × (1e+9 / 425.1437075) = 35282187.49421335