Questions & Answers about Машина не едет, нам нужно топливо.
Why do we use нужно instead of нужен?
The word нужен acts like a short adjective and must agree in gender and number with the thing being needed. Since топливо (fuel) is a neuter noun, it takes the neuter form нужно.
Why is 'we' translated as нам rather than мы?
When expressing need with нужен, the person who needs the object takes the dative case. Нам is the dative form of мы. The literal structure is closer to 'To us, fuel is necessary.'
Why use едет instead of a different verb of motion like идёт or ездит?
Едет is the present tense of ехать, which is the verb for one-way motion by a vehicle. You cannot use идёт because that means moving on foot, and ездит implies habitual or multi-directional driving, whereas this car is stuck right now.
Can I use топливо to say I need 'gasoline' or 'petrol'?
Топливо translates specifically to the broad category of 'fuel'. While it works perfectly here, in everyday conversation a Russian speaker would usually say бензин when talking about needing regular car gas.