The difficulty occurs I think because of the following.

What UKers call petrol is what North Americans call gasoline. However, gasoline is often shortened to gas as in 'put some gas in the car.' We should be saying 'put some gasoline in the car.'

Furnaces/fireplaces use natural gas and on occasion propane.

To avoid confusion on emergency scenes I've worked, we called a spade a spade. That means natural gas was called natural gas, propane called propane and gasoline called gasoline.

I hope that helps.