Example:
15 nautical mile per US gallon = 7.343633e-9 Tm/L
1 nautical mile per US gallon = 4.895755e-10 Tm/L | 1 Tm/L = 2.042586e+9 nautical mile per US gallon
Conversion Steps:
15 × (489.5755247 / 1e+12) = 7.343633e-9