Antes da viagem, eu quero escolher a bomba com o combustível mais barato.

Because da is the normal contraction of de + a.

• antes de = before
• a viagem = the trip

So:

• antes de + a viagem → antes da viagem

This is very common in Portuguese. You will often see these contractions:

• de + o = do
• de + a = da
• de + os = dos
• de + as = das

Here, viagem is a feminine noun, so a viagem becomes da viagem after de.

Yes, you can absolutely say Quero escolher...

In Portuguese, subject pronouns are often omitted because the verb ending already shows who the subject is.

• eu quero = I want
• quero = still clearly means I want in most contexts

Including eu can add:

• emphasis
• contrast
• clarity

So:

• Quero escolher a bomba... = very natural
• Eu quero escolher a bomba... = also natural, but slightly more explicit or emphatic

This is especially common in European Portuguese, where subject pronouns are often left out unless needed.

Because after querer when you say you want to do something, Portuguese normally uses the infinitive.

The pattern is:

• querer + infinitive

Examples:

• quero comer = I want to eat
• quero sair = I want to leave
• quero escolher = I want to choose

So escolher stays in the infinitive because it depends on quero.

Yes, bomba can mean bomb, but here it means fuel pump or petrol pump.

In Portugal, in the context of a petrol station, bomba is commonly used for the pump where you fill the car.

So depending on context:

• uma bomba = a bomb
• uma bomba de combustível / bomba de gasolina = a fuel pump / petrol pump
• simply a bomba can also mean the pump if the context is obvious

This is a good example of how context determines meaning.

This means the pump with the cheapest fuel.

The structure is:

• a bomba = the pump
• com = with
• o combustível mais barato = the cheapest fuel

So com o combustível mais barato describes which pump you mean: the one associated with the lowest-priced fuel.

In natural English, you might think of it as:

• the pump that has the cheapest fuel
• the pump with the cheapest fuel

Portuguese often uses com this way to attach a characteristic to a noun.

Because barato agrees with combustível, not with bomba.

Here is the key part:

• o combustível mais barato

Since combustível is masculine singular, the adjective must also be masculine singular:

• barato

If the noun were feminine, it would change:

• a gasolina mais barata

So:

• combustível → masculine singular → mais barato
• gasolina → feminine singular → mais barata

Yes, and that may actually sound clearer to many learners.

Compare:

• a bomba com o combustível mais barato
• a bomba que tem o combustível mais barato

Both are grammatical. The second version is a bit more explicit because it spells out the relationship with que tem (that has).

The original sentence is perfectly fine, but que tem can feel easier to understand if you are still getting used to Portuguese noun phrases.

Not exactly.

combustível means fuel in a general sense.

It could refer to:

• gasolina = petrol / gasoline
• gasóleo = diesel
• other types of fuel as well

So combustível is broader than gasolina.

In Portugal:

• gasolina = petrol
• gasóleo = diesel

If you want to be specific, you would use one of those words instead of the general word combustível.

Yes, it is grammatical and understandable in European Portuguese.

That said, depending on the situation, a native speaker might also say something a little more specific, for example:

• Antes da viagem, quero escolher a bomba com a gasolina mais barata.
• Antes da viagem, quero escolher o posto com o combustível mais barato.

Why? Because in real life, people often compare:

• a type of fuel
• a petrol station (posto)
• prices across stations

rather than just a pump in isolation

So the original sentence is correct, but the most natural wording depends on the exact context.

Because Antes da viagem is an introductory time expression placed at the beginning of the sentence.

The comma helps separate that opening phrase from the main clause:

• Antes da viagem, eu quero escolher...

This is similar to English punctuation in sentences like:

• Before the trip, I want to...

In short:

• the comma is natural and correct
• it marks the introductory phrase
• sometimes in short sentences people may omit such commas informally, but here the comma is standard and helpful

Yes. Portuguese allows some flexibility.

For example:

• Antes da viagem, eu quero escolher a bomba com o combustível mais barato.
• Eu quero escolher a bomba com o combustível mais barato antes da viagem.

Both are possible, but the emphasis changes slightly.

• Antes da viagem at the start emphasizes the time first.
• Putting it later makes the sentence begin with what I want rather than when.

Starting with Antes da viagem is very natural if the timing is important.

In European Portuguese, the stress falls on -tí-:

• com-bus-TÍ-vel

A few things to notice:

• the written accent in combustível shows the stressed syllable
• European Portuguese often reduces unstressed vowels, so some vowels may sound weaker than an English speaker expects
• the final -vel is not pronounced like English vell in a strong, full way; it is more reduced

A useful learning point is: whenever you see an accent mark like í, it tells you where the stress goes.