Antes de pegar a estrada, eu vou colocar gasolina no carro.

Because when antes is followed by a verb, Portuguese normally uses de before the infinitive:

• antes de sair = before leaving
• antes de comer = before eating
• antes de pegar a estrada = before hitting the road

If antes is followed by a noun or a full clause, the structure can be different:

• antes do almoço = before lunch
• antes que eu saia = before I leave

So in your sentence, pegar is a verb, which is why you get antes de pegar.

It is an idiomatic expression. Literally, pegar often means to take, to grab, or to catch, but pegar a estrada means:

• to hit the road
• to set out by car
• to start a road trip / drive off

So it does not mean physically grabbing a road. It is a very natural expression in Brazilian Portuguese.

Portuguese often uses the definite article where English would not. In this expression, pegar a estrada is the normal form.

This is common in Portuguese:

• pegar o ônibus = take the bus
• abrir a porta = open the door
• pegar a estrada = hit the road

Even if English says hit the road without much focus on a specific road, Portuguese still naturally uses a here.

In Brazilian Portuguese, ir + infinitive is one of the most common ways to talk about the future.

• eu vou colocar gasolina = I’m going to put gas in / I’ll put gas in
• eu colocarei gasolina = I will put gas in

The simple future (colocarei) is grammatically correct, but in everyday spoken Brazilian Portuguese, vou colocar sounds more natural and common.

Yes. In Brazilian Portuguese, subject pronouns are often optional, especially when the verb form already makes the subject clear.

So these both work:

• Antes de pegar a estrada, eu vou colocar gasolina no carro.
• Antes de pegar a estrada, vou colocar gasolina no carro.

Including eu can add emphasis, clarity, or a more explicit subject. Omitting it often sounds a bit more natural in casual speech.

Because no is a contraction:

• em + o = no

This kind of contraction is extremely common in Portuguese:

• em + a = na
• de + o = do
• de + a = da
• a + o = ao

So:

• colocar gasolina no carro = put gas in the car

You should think of no as a normal, expected form here.

Because Portuguese often uses the broader idea of putting gas into the car rather than explicitly saying into the tank.

So:

• colocar gasolina no carro is natural
• it means putting fuel into the car’s fuel system/tank

If you wanted to be more specific, you could say:

• colocar gasolina no tanque = put gas in the tank

But in everyday speech, no carro is perfectly understandable and natural.

It is understandable and natural enough, but many Brazilians would more commonly say:

• abastecer o carro = fill up the car / refuel the car
• colocar gasolina = put gas in / add gasoline

So your sentence is fine, but a very common alternative would be:

• Antes de pegar a estrada, vou abastecer o carro.

Both are good; abastecer just sounds a bit more idiomatic for fueling a vehicle.

The part Antes de pegar a estrada is an introductory phrase. In Portuguese, it is common to put a comma after an introductory phrase before the main clause:

• Antes de sair, vou te ligar.
• Depois do almoço, a gente conversa.

So the comma helps separate:

1. the time expression: Antes de pegar a estrada
2. the main action: eu vou colocar gasolina no carro

You may sometimes see commas omitted in informal writing, but with this structure, the comma is standard and helpful.

Yes, you can:

• Antes de pegar a estrada
• Antes de eu pegar a estrada

Both are possible.

The version without eu is usually more concise and very common when the subject is understood. The version with eu can add emphasis or make the subject more explicit.

In many everyday situations, antes de pegar a estrada is the more natural choice.

In Brazilian Portuguese, gasolina specifically means gasoline/petrol.

English can be tricky here because gas in American English means gasoline, but in Portuguese:

• gasolina = gasoline/petrol
• gás = gas, such as cooking gas or natural gas

So gasolina is the correct word for fuel for a gasoline-powered car.

Not in this sentence if you mean fueling the car.

• colocar gasolina no carro = put gas in the car
• colocar gasolina para o carro would sound unnatural here

Para o carro usually suggests for the car, not into the car. The action of inserting fuel requires em, which contracts to no.

It is the infinitive:

• pegar = to take / to hit (in this expression)

After antes de, Portuguese normally uses the infinitive when the subject is general or understood:

• antes de sair
• antes de dormir
• antes de pegar a estrada

So even though the sentence refers to a future action, the verb after antes de stays in the infinitive.

The original sentence is good, but a very natural everyday version would be:

• Antes de pegar a estrada, vou colocar gasolina no carro.

That version drops eu, which is very common.

Another very idiomatic option is:

• Antes de pegar a estrada, vou abastecer o carro.

So your sentence is correct, and there are just slightly more conversational alternatives depending on style.