Αν το ρεζερβουάρ είναι σχεδόν άδειο, κάνεις πολλή ώρα να βρεις βενζινάδικο ανοιχτό το βράδυ.

Αν means if.

In this sentence, Αν το ρεζερβουάρ είναι σχεδόν άδειο... gives a general condition: if the tank is almost empty.... Greek often uses the present tense in both parts for general truths or typical situations, just like English can say If the tank is almost empty, it takes a long time...

So this is not talking about one specific future event only; it sounds more like a general observation.

Το ρεζερβουάρ is neuter singular.

• το = the neuter singular article
• ρεζερβουάρ = reservoir / tank, here fuel tank

In this sentence it is the subject of είναι, so it is in the nominative. For many neuter nouns, the nominative and accusative look the same anyway.

Also, ρεζερβουάρ is a loanword, so it does not change much in form.

Because άδειο must agree with το ρεζερβουάρ, which is neuter singular.

So:

• άδειος = masculine
• άδεια = feminine
• άδειο = neuter

Since ρεζερβουάρ is neuter, the adjective is also neuter: άδειο.

Σχεδόν means almost and does not change form.

Yes, literally it looks like you make a lot of time, but as an expression it means:

it takes you a long time to...

So:

• κάνω ώρα να... = take time to...
• κάνω πολλή ώρα να... = take a long time to...

This is a very common Greek structure.

A close natural English translation is:

• you take a long time to find...
• or more idiomatically, it takes a long time to find...

Because here πολλή is an adjective modifying ώρα, and ώρα is a feminine singular noun.

So the adjective has to agree:

• πολλός = masculine
• πολλή = feminine
• πολύ = neuter / adverb

Since ώρα is feminine, Greek uses πολλή ώρα = a lot of time / a long time.

Compare:

• πολλή ώρα = a long time
• πολύ αργά = very late

In the second example, πολύ is an adverb, so it stays πολύ.

Not necessarily a specific you. Greek often uses the second person singular the same way English uses you in a general sense:

• If the tank is almost empty, you take a long time to find...

This means anyone / people in general, not only one specific person.

So κάνεις here is a generic you.

Greek could also express this more impersonally, but this version is very natural and common.

After expressions like κάνω ώρα, Greek commonly uses να + verb.

So:

• κάνω ώρα να βρω = I take time to find
• κάνεις ώρα να βρεις = you take time to find

This is a normal Greek pattern:

• main verb + να
  • another verb

Here να introduces the action that takes time.

Because να βρεις uses the aorist subjunctive, which usually points to a single completed result: to manage to find / to find.

That fits the meaning here well:

• you spend a long time until you find an open gas station

If Greek used να βρίσκεις, it would sound more ongoing, repeated, or process-focused. In this sentence, the important idea is reaching the result: finding one.

So:

• να βρεις = to find, as a completed outcome
• να βρίσκεις = to be finding / to find repeatedly or as an ongoing process

Yes. Βρεις comes from the verb βρίσκω = I find.

This verb has an irregular-looking aorist stem:

• present: βρίσκω
• aorist: βρήκα
• aorist subjunctive: να βρω, να βρεις, να βρει...

So να βρεις means for you to find / to find.

This change of stem is normal for many common Greek verbs, so it is worth learning as a principal form.

Greek has no indefinite article like English a/an.

So a bare noun can often mean a ... in English.

Here:

• να βρεις βενζινάδικο = to find a gas station

Greek could also say να βρεις ένα βενζινάδικο, but ένα is not always required. Adding ένα can make it a little more explicit or emphatic.

So both are possible, but the version without ένα is very natural.

Ανοιχτό means open, and it agrees with βενζινάδικο, which is also neuter singular.

So:

• βενζινάδικο ανοιχτό = an open gas station

Greek adjectives can come after the noun much more freely than in English. That position is very common, especially when the adjective feels descriptive or closely tied to the situation.

Here the order sounds natural and emphasizes the practical idea:

• finding a gas station
• and specifically one that is open

Again, this is agreement.

Βενζινάδικο is neuter singular, so the adjective must also be neuter singular:

• ανοιχτός = masculine
• ανοιχτή = feminine
• ανοιχτό = neuter

So βενζινάδικο ανοιχτό is grammatically correct.

In this sentence, το βράδυ means something like at night / in the evening depending on context.

Literally it is the evening/night, but Greek often uses this kind of expression as a time expression without a preposition:

• το πρωί = in the morning
• το απόγευμα = in the afternoon
• το βράδυ = in the evening / at night

Here it modifies the situation of the gas station being open, so the idea is:

• an open gas station at night

English wording may vary, but the Greek is very natural.

It mainly goes with the whole idea of finding a gas station that is open at night.

In other words, the natural interpretation is not just:

• find a gas station but:
• find a gas station open at night

Because of word order, ανοιχτό το βράδυ feels like one unit: open at night.

So το βράδυ is closely linked to ανοιχτό.

Because Greek normally drops subject pronouns when the verb ending already shows the person.

Here:

• κάνεις already means you do / you take
• είναι already means it is

So Greek does not need εσύ unless the speaker wants emphasis or contrast.

For example:

• Εσύ κάνεις πολλή ώρα... = You are the one who take(s) a long time... / You, specifically...

Without the pronoun, the sentence is more neutral and natural.

Yes. That would also be natural, but the structure changes slightly.

For example:

• Παίρνει πολλή ώρα να βρεις βενζινάδικο ανοιχτό το βράδυ. = It takes a long time to find a gas station open at night.

Compare:

• Κάνεις πολλή ώρα να βρεις...
  = You take a long time to find...
• Παίρνει πολλή ώρα να βρεις...
  = It takes a long time to find...

Both are common. The original sentence uses the more personal, generic-you style.

Greek word order is fairly flexible, though not completely free.

This sentence is natural as written because it keeps related words together:

• βενζινάδικο ανοιχτό το βράδυ

But Greek could move parts around for emphasis. For example:

• Αν το ρεζερβουάρ είναι σχεδόν άδειο, κάνεις πολλή ώρα να βρεις το βράδυ βενζινάδικο ανοιχτό.

That is grammatically possible, but less natural in ordinary speech.

So the given order is good because it sounds smooth and clearly expresses:

• first the condition
• then the delay
• then the goal: find a gas station open at night