The most essential difference, as a user, is the boiling temperature of both products. This is the temperature where the product goes from its liquid state to its gaseous state. Propane boils and vaporizes at -42°C, while butane boils at 1°C. You use the vapor, in other words the gas. For example: A butane gas cylinder which is stocked outside at a temperature or -5°C will not produce any gas becaus it will not be able to reach the boiling point. For more properties of propane and butane gas please go to www.propaangas.be.