Gas is a short form of gasoline and also is a word for gaseous form substance as oxygen for example and also we can make liquid gas as propane for example. The problem is all of these words can designate different kind of fuel. The question is how should I ask what kind of fuel some car is using? I was in Asia and they use two kinds of fuel which are gas and... gas! And I tried to ask my taxi driver something like that "Does your car use gas or gas?" which is a weird question. Can I ask "Does your car use gasoline or gas?" and more important can native American English speaker understand what I mean in this question? Or maybe there is another way to ask this question?
To most effectively ask someone what type of fuel their vehicle uses, I would advise using the sentence, "What type of fuel does your car use/take?" This is by far the most direct and doesn't leave much interpretation to the listener. It doesn't have words with multiple meanings that will lead to confusion, nor gives the listener something to ponder besides what the meaning of fuel is. Granted, there really is one general definition of fuel, which is something that is used to power a car. Hopefully this helps you with your question.