Przed wyjazdem muszę zatankować samochód.

Because przed requires the instrumental case when it means before in a time sense.

• base form: wyjazd = departure / leaving / trip
• instrumental singular: wyjazdem

So:

• przed wyjazdem = before the departure / before leaving

This is a very common pattern in Polish:

• przed pracą = before work
• przed snem = before sleep
• przed podróżą = before the trip

Wyjazd most literally means departure, leaving, or sometimes a trip away.

In this sentence, przed wyjazdem most naturally means:

• before leaving
• before the trip
• before departure

Which English translation fits best depends on context. If someone is about to drive somewhere, it may feel like before the trip. If the focus is simply on the act of leaving, then before leaving is closer.

Muszę is the 1st person singular form of musieć = to have to / must.

So:

• muszę = I must / I have to

Polish commonly uses this present-tense form with an infinitive to express obligation:

• muszę iść = I have to go
• muszę kupić chleb = I have to buy bread
• muszę zatankować samochód = I have to refuel the car

This is mainly about aspect.

• tankować = imperfective
• zatankować = perfective

In this sentence, zatankować is natural because the speaker means one complete action that needs to be done before leaving.

So muszę zatankować samochód suggests:

• I need to refuel the car
• I need to get that done

If you said muszę tankować samochód, it would sound less natural in this context, because the imperfective usually focuses more on the process, repetition, or ongoing action.

A useful rule of thumb:

• perfective = completing the action
• imperfective = process / habit / repetition / general activity

Because samochód is the direct object of zatankować, so it goes in the accusative case.

For masculine inanimate nouns like samochód, the accusative singular is the same as the nominative singular:

• nominative: samochód
• accusative: samochód

So the form does not change, even though the case does.

Compare that with a masculine animate noun, where accusative often looks different:

• widzę psa = I see the dog

But:

• zatankować samochód = to refuel the car

Yes. If the context is clear, Polish often omits the object.

So you can say:

• Przed wyjazdem muszę zatankować.

That would naturally mean something like:

• Before leaving, I need to refuel.
• Before the trip, I need to fill up.

The listener will usually understand that you mean the car.

Usually it means to put fuel into the car or to refuel the car. In many contexts, English would naturally say fill up the car.

However, zatankować does not always explicitly mean filling it completely to full. It often just means to refuel.

If you want to be very specific and say fill it all the way up, Polish can say:

• zatankować do pełna = fill up completely / fill the tank

So:

• muszę zatankować samochód = I need to refuel the car
• muszę zatankować samochód do pełna = I need to fill the car up completely

No. Polish word order is fairly flexible, because case endings show grammatical relationships.

The original sentence:

• Przed wyjazdem muszę zatankować samochód.

is very natural.

But you could also say:

• Muszę zatankować samochód przed wyjazdem.
• Samochód muszę zatankować przed wyjazdem.

These versions are all understandable, but they shift the emphasis a little:

• Przed wyjazdem first = emphasizes the time
• Muszę first = emphasizes the obligation
• Samochód first = emphasizes the object

The original version sounds neutral and natural.

Yes, but the structure would have to change.

• przed wyjazdem uses przed + noun
• zanim introduces a clause

So you can say:

• Przed wyjazdem muszę zatankować samochód.
• Zanim wyjadę, muszę zatankować samochód.

These are very close in meaning:

• przed wyjazdem = before the departure / before leaving
• zanim wyjadę = before I leave

So the difference is grammatical, not big in meaning.

Yes. Auto is also very common and natural in everyday Polish.

So you can say:

• Przed wyjazdem muszę zatankować auto.

Both are correct:

• samochód = car
• auto = car

Auto often sounds a little more casual and conversational.

No. Zatankować is a general verb meaning to refuel. It does not by itself specify the type of fuel.

Depending on the vehicle, it could mean adding:

• petrol / gasoline
• diesel
• another fuel

If needed, Polish can specify the fuel separately, for example:

• zatankować benzynę is not the usual way to say it
• more natural is to say something like zatankować samochód benzyną or simply specify at the station what fuel you want

In the sentence you gave, the important idea is just refuel the car before leaving.