Self-tutoring about common fuels: the tutor makes an initial comparison of natural gas to propane.
Natural gas is chiefly methane, CH4; propane is C3H8.
The combustion equation for methane:
CH4 + 2O2 → CO2 + 2H2O
Propane’s combustion equation, on the other hand, is
C3H8 + 5O2 → 3CO2 + 4H2O
Therefore, methane uses 2/5, or 40% as much oxygen as propane to combust; its heat value is about 40% of propane’s as well (38.7 vs 93.2 MJ/m3).
Source:Oracle Tutoring by Jack and Diane, Campbell River, BC.