Ako cijena goriva opet naraste, radije ćemo ići autobusom u grad.

In Croatian, after ako for a real, possible future condition, you normally use the present tense, not će + infinitive.

So Croatian says:

Ako cijena goriva opet naraste, ...

literally using a present form, even though the meaning is future: If the fuel price rises again...

This is similar to natural English, where we also say If it rains tomorrow, we'll stay home, not If it will rain tomorrow.

So the pattern here is:

ako + present → main clause in future

Naraste is the 3rd person singular present form of narasti.

• narasti = to grow, rise, increase
• naraste = it rises / it grows

Here the subject is cijena (price), which is singular, so the verb is also singular:

• cijena ... naraste = the price ... rises

In this sentence, naraste is best understood as goes up / increases.

Because narasti and rasti are different in aspect.

• rasti = imperfective
• narasti = perfective

In sentences like this, Croatian often uses a perfective present after ako to talk about a future event that would happen as a whole:

• Ako cijena goriva naraste... = If the fuel price goes up...

Using raste would sound more like an ongoing process or general rising, while naraste fits better for a single future increase.

Because Croatian often uses the genitive after a noun to show of relationships.

So:

• cijena = price
• goriva = of fuel

Together:

• cijena goriva = the price of fuel

Here gorivo is a neuter noun, and goriva is its genitive singular form.

This is a very common pattern in Croatian:

• boja auta = the color of the car
• vrata kuće = the door of the house
• cijena karte = the price of the ticket

Because gorivo is usually treated as a mass noun, like fuel in English.

So cijena goriva means the price of fuel in a general sense.

Croatian often uses the singular for substances and mass nouns:

• voda = water
• mlijeko = milk
• gorivo = fuel

If the context were about different fuel prices or several separate prices, a plural structure might appear, but here singular is the normal choice.

Opet means again.

So:

• opet naraste = rises again

Its position is somewhat flexible, but the placement here is very natural. Putting it before the verb makes the meaning clear and neutral.

You may also see ponovno, which also means again, but opet is very common in everyday speech.

Radije means rather or preferably.

In this sentence:

• radije ćemo ići autobusom = we’ll rather go by bus
• more natural English: we’d prefer to go by bus

It expresses preference between options, even if the other option is not stated explicitly. The unstated idea is something like:

• rather than driving
• rather than spending more on fuel

So radije is the word that adds the idea of preference.

This is the future tense in Croatian, often called future I.

It is formed with:

htjeti in its short auxiliary form + infinitive

Here:

• ćemo = we will
• ići = to go

So:

• ćemo ići = we will go

The full set is:

• ću
• ćeš
• će
• ćemo
• ćete
• će

Examples:

• Ići ću = I will go
• Ići ćemo = we will go

Because ćemo is a clitic, and Croatian clitics usually like to stand near the second position in the clause.

So in:

radije ćemo ići autobusom u grad

the first important element is radije, and ćemo comes right after it.

This is very normal Croatian word order.

Other word orders are possible, but they may sound different in emphasis. The version in your sentence is natural and standard.

Autobusom is the instrumental singular of autobus.

Croatian uses the instrumental case to express the means of transport, usually without a preposition:

• ići autobusom = go by bus
• ići vlakom = go by train
• ići autom = go by car

So autobusom answers the question how? / by what means?

This is one of the most common uses of the instrumental in Croatian.

Because Croatian distinguishes between:

• movement toward a place → u + accusative
• location in a place → u + locative

So:

• u grad = to town / into the city
• u gradu = in the town / in the city

Since the sentence is about going somewhere, Croatian uses u grad.

Compare:

• Idemo u grad. = We’re going to town.
• Mi smo u gradu. = We are in town.

Because Croatian has no articles.

English needs words like the fuel price, a bus, the city, but Croatian usually expresses definiteness through context, word order, and meaning.

So:

• cijena goriva can mean the price of fuel
• autobusom can mean by bus
• u grad can mean to town or to the city

You understand which one is meant from the situation, not from a separate word like the or a.

Yes. The clause beginning with ako comes first, and it is separated from the main clause by a comma:

Ako cijena goriva opet naraste, radije ćemo ići autobusom u grad.

So the structure is:

• subordinate clause: Ako cijena goriva opet naraste
• main clause: radije ćemo ići autobusom u grad

That comma is standard Croatian punctuation here.