O depósito está quase vazio, por isso vou parar na bomba de gasolina antes de entrar na estrada principal.

In this sentence, o depósito means the tank, specifically the car’s fuel tank.

This is a good example of a false friend:

• English deposit usually means money paid into a bank, or money paid in advance.
• Portuguese depósito can mean that too, but it can also mean a tank, container, or reservoir.

So here, O depósito está quase vazio means the fuel tank is almost empty.

Portuguese uses estar for states or conditions, and ser for identity or more permanent characteristics.

Here, quase vazio describes the current condition of the tank, so estar is the natural choice:

• O depósito está quase vazio = the tank is almost empty

You would not normally say é quase vazio here, because being empty is not seen as the tank’s essential nature; it is just its present state.

Quase vazio means almost empty.

• quase = almost
• vazio = empty

Vazio is an adjective, so it does not need an article here. It simply describes the noun through estar.

The structure is:

• O depósito = the tank
• está = is
• quase vazio = almost empty

This is very similar to English: The tank is almost empty.

Por isso means therefore, so, or for that reason.

It links the first idea to the result:

• O depósito está quase vazio → the tank is almost empty
• por isso vou parar... → so I’m going to stop...

It is a very common connector in Portuguese. You can think of it as introducing a consequence.

Other possible connectors with a similar role are:

• por isso
• por essa razão
• por conseguinte (more formal)
• então (often more conversational, depending on context)

In this sentence, por isso is very natural.

The comma separates two related clauses:

• O depósito está quase vazio
• por isso vou parar na bomba de gasolina...

This is normal in Portuguese when a connector such as por isso introduces the consequence of the previous clause.

In writing, the comma helps show the pause and the logical link:

• cause: the tank is almost empty
• result: I’m going to stop for petrol

Vou parar is the very common near future construction in Portuguese:

• vou = I go / I am going
• parar = to stop

Together:

• vou parar = I’m going to stop / I will stop

Although Portuguese does have a simple future form:

• pararei = I will stop

in everyday speech, especially in conversation, ir + infinitive is often more natural and more common.

So:

• vou parar sounds everyday and conversational
• pararei is correct, but often sounds more formal or less spontaneous

Portuguese often omits subject pronouns when the verb ending already makes the subject clear.

Here:

• vou clearly means I am going

So (eu) vou parar is usually shortened to just vou parar.

This is very common in Portuguese:

• Vou sair = I’m going out
• Tenho fome = I’m hungry
• Preciso de gasolina = I need petrol

You can include eu for emphasis or contrast, but it is not necessary here.

Na is a contraction of:

• em = in / at
• a = the

So:

• na = in the or at the, depending on context

Here:

• na bomba de gasolina = at the petrol pump / at the petrol station

Portuguese uses these contractions all the time:

• em + o = no
• em + a = na
• em + os = nos
• em + as = nas

So na estrada principal later in the sentence works the same way:

• em + a estrada principal → na estrada principal

Strictly speaking, bomba de gasolina literally means petrol pump.

In real usage, though, people may sometimes use it loosely when talking about stopping for fuel. That said, in European Portuguese, posto de gasolina is often the clearer and more usual way to say petrol station.

So:

• bomba de gasolina = petrol pump
• posto de gasolina = petrol station

In this sentence, parar na bomba de gasolina is understandable, but many learners will also hear or see:

• vou parar no posto de gasolina

That is often the more natural choice if you mean the whole station rather than the pump itself.

After antes, Portuguese normally uses de before an infinitive:

• antes de entrar = before entering / before I enter

So the pattern is:

• antes de + infinitive

Examples:

• antes de sair = before leaving
• antes de comer = before eating
• antes de dormir = before sleeping

This is a very common structure and should be learned as a set pattern.

It is in the infinitive because after antes de, Portuguese commonly uses the infinitive when the subject is the same as in the main clause.

Here, the person who is going to stop is also the person who is going to enter the main road:

• vou parar = I’m going to stop
• antes de entrar = before entering

Because the subject is the same, Portuguese does not need a finite verb here.

If you want to make the subject explicit and different, Portuguese can use a personal infinitive or another structure, for example:

• antes de eu entrar = before I enter
• antes de eles entrarem = before they enter

Yes. Na is again em + a.

So:

• na estrada principal = on the main road / onto the main road, depending on context

The noun phrase is:

• estrada = road
• principal = main

Together:

• estrada principal = main road

This is a normal noun + adjective order in Portuguese.

In Portuguese, adjectives often come after the noun, much more often than in English.

So:

• estrada principal = main road
• carro vermelho = red car
• tanque vazio / depósito vazio = empty tank

Some adjectives can go before the noun, but the position may change the tone, emphasis, or even the meaning. With principal, the usual neutral order here is after the noun:

• estrada principal

That is the most natural choice in this sentence.

It usually corresponds well to main road, but the exact English translation can depend on context.

In European Portuguese:

• estrada is a general word for road
• estrada principal means the main road in the area or route being discussed

It does not necessarily mean a motorway. If you wanted to say motorway, Portuguese would more likely use:

• autoestrada

So:

• estrada principal = main road
• autoestrada = motorway / highway

That distinction is useful for learners, because English road, main road, and highway do not always match Portuguese one-to-one.

Yes. The sentence is understandable, but some speakers might prefer a version like:

• O depósito está quase vazio, por isso vou parar num posto de gasolina antes de entrar na estrada principal.

Why?

• num posto de gasolina often sounds more natural if you mean at a petrol station
• na bomba de gasolina can sound more specifically like at the pump

Both are understandable, but posto de gasolina is often the safer expression for learners in European Portuguese.