Example:
15 nautical mile per US gallon = 0.000007 Gm/L
1 nautical mile per US gallon = 4.895755e-7 Gm/L | 1 Gm/L = 2042585.769811 nautical mile per US gallon
Conversion Steps:
15 × (489.5755247 / 1e+9) = 0.000007344