¿Podría usted decirme si la gasolinera más cercana está antes del peaje?

Podría makes the request more polite and less direct. It is like saying Could you tell me... rather than Can you tell me...

• ¿Puede usted decirme...? = polite
• ¿Podría usted decirme...? = even more polite / softer

In directions or when asking strangers for help, this more formal, courteous style is very common.

Usted is the formal word for you. It shows respect, especially with strangers.

In this sentence, usted is not strictly necessary, because the verb form podría already shows that the speaker is addressing usted. So both are possible:

• ¿Podría usted decirme...?
• ¿Podría decirme...?

Including usted makes the sentence sound a bit more formal or emphatic.

Decirme is decir + me:

• decir = to tell
• me = to me

So decirme means to tell me.

After a conjugated verb like podría, Spanish often allows two structures:

• ¿Podría decirme...?
• ¿Me podría decir...?

Both mean the same thing. In your sentence, the pronoun is attached to the infinitive decir.

Here si means whether, not a real conditional if.

So:

• decirme si... = tell me whether...

In English, we often say if in this kind of sentence:
Could you tell me if the nearest petrol station is before the toll?

Spanish uses si in the same way for indirect yes/no questions.

In Spanish, adjectives usually come after the noun, and that also applies to expressions like más cercana.

So the normal order is:

• la gasolinera más cercana = the nearest petrol station

Breaking it down:

• la gasolinera = the petrol station
• más cercana = nearer / nearest

Spanish normally places más + adjective after the noun in this kind of phrase.

Está is used because the sentence is asking about location.

• estar = to be, for location or temporary states
• ser = to be, for identity, description, origin, etc.

Since the question is about where the petrol station is in relation to the toll, Spanish uses estar:

• La gasolinera está antes del peaje. = The petrol station is before the toll.

Antes de means before.

When de is followed by el, they combine:

• de + el = del

So:

• antes del peaje = before the toll

Peaje can refer to the toll itself, the toll point, or the toll booth area, depending on context. In road directions, it usually means the toll point you reach on the road.

Because in Spanish, de + el contracts to del.

So:

• antes de el peaje ❌
• antes del peaje ✅

This contraction is mandatory, except when el is part of a proper name.

Yes. In Spain, gasolinera is a very common everyday word for a petrol station.

You may also hear:

• estación de servicio = service station / petrol station

But gasolinera is very natural and common in Spain.

Spanish uses question marks at both the beginning and the end of a direct question:

• ¿ ... ?

So this is correct:

• ¿Podría usted decirme si la gasolinera más cercana está antes del peaje?

English only marks the end, but Spanish marks both ends.

It sounds quite formal and very polite. The formality comes from:

• podría instead of a more direct verb
• usted
• the full, careful structure decirme si...

This is the kind of sentence you might use with:

• a stranger
• an employee
• a police officer
• an older person

In a less formal situation, you might hear:

• Perdone, ¿la gasolinera más cercana está antes del peaje?
• ¿Me puede decir si la gasolinera más cercana está antes del peaje?

Yes. La estación de servicio más cercana is also correct.

The difference is mainly style and usage:

• gasolinera = very common, everyday
• estación de servicio = slightly more neutral or formal-sounding

In Spain, both are understood perfectly.

Yes. The adjective has to agree with gasolinera, which is singular and feminine.

So:

• la gasolinera más cercana = singular feminine

Compare:

• el hotel más cercano = singular masculine
• las gasolineras más cercanas = plural feminine
• los hoteles más cercanos = plural masculine

The más part does not change, but cercano/cercana/cercanos/cercanas does.

You could, but the meaning changes.

• la gasolinera más cercana = the nearest petrol station
• la gasolinera cercana = the nearby petrol station

Más cercana clearly expresses nearest, so it is the better choice here.

The whole sentence is a direct question, because it asks someone something directly and has question marks.

Inside it, si la gasolinera más cercana está antes del peaje is an indirect yes/no question, introduced by si.

So you can think of it like this:

• Main direct question: ¿Podría usted decirme ... ?
• Embedded indirect question: ... si la gasolinera más cercana está antes del peaje

Yes, but it is on the careful, polite, formal side. It sounds natural, especially if you are being respectful.

In casual speech, many people would shorten it a bit, for example:

• Perdone, ¿sabe si la gasolinera más cercana está antes del peaje?
• ¿Me puede decir si la gasolinera más cercana está antes del peaje?

Your original sentence is absolutely correct and useful, especially for polite communication.