While Australia is not as divided by two common languages as the UK and US, we are still somewhat divided from the US here.
A line from a novel. "I've got Blue Cross". That'd be health insurance. Another, "I've got gas". The latter would refer to wind, burping or farting I suppose.
Every few months we buy gas. That is for our barbeque. There are still some cars around that use gas as fuel and some service stations that have gas bowsers. In the US, buying gas would be more frequent, to fill a car with fuel.
Our gas is LPG, Liquid Propane Gas, for a few cars, barbeques and camping lights and camping stoves. Natural gas is what comes through pipes for your hotplates and oven unless you are in the country and buy bottled gas, which is LPG. As in the US gas is petrol for a vehicle, they can't use gas for LPG, so it is called just Propane. I'd be quite happy with using that here but I would not be happy calling petrol, gas. Petrol is a liquid after all.
Where to you buy petrol/gas in the US? We buy it at a petrol station or a service station, abbreviated to a servo. Are you confused? I am.