Fuel – le carburant
(Pronounced carb-you-ron – the "n" is barely sounded and the "t" is silent, as in restaurant)
Her body lacked fuel. Her friend said: "It's that low carb diet you're on! Can I fill you up with some diesel or petrol?"
Carburant is masculine, so it's le carburant. Imagine our early learner filling up his car with fuel.