Devo rifornire l’auto di benzina prima di prendere l’autostrada.

Devo means I must, I have to, or I need to.

It is the 1st person singular form of dovere (to have to / must):

• io devo = I have to
• tu devi = you have to
• lui/lei deve = he/she has to

In this sentence, devo rifornire... means I need to refuel... or I have to fill up...

Here rifornire means to refuel or to supply with fuel.

So:

• rifornire l’auto = to refuel the car

It is a bit more formal or standard than everyday spoken alternatives. In conversation, Italians very often say:

• fare benzina = to get gas / to fill up

So a very natural everyday version of the sentence would be:

• Devo fare benzina prima di prendere l’autostrada.

Because auto is being used with the definite article la (the), and la becomes l’ before a vowel.

So:

• la auto → l’auto

This is called elision.

The same thing happens with:

• la autostrada → l’autostrada

In Italian, after rifornire you commonly use di to say what something is being supplied with.

So:

• rifornire l’auto di benzina = to fill/refuel the car with gasoline

Literally, it is like to supply the car with gasoline.

English learners may expect con because English uses with, but with rifornire, di is the normal choice.

Yes, in meaning it corresponds to gas or gasoline in American English, and petrol in British English.

So:

• benzina = gas / gasoline / petrol

Be careful not to confuse it with gas in the broader scientific sense. In Italian, benzina specifically means the fuel for cars that run on gasoline.

Prima di means before when it is followed by a verb in the infinitive.

Structure:

• prima di + infinitive

So:

• prima di prendere l’autostrada = before taking the motorway

Compare:

• Prima di uscire, chiudi la porta. = Before going out, close the door.
• Prima di mangiare, lavati le mani. = Before eating, wash your hands.

If a full clause follows instead, Italian often uses prima che + subjunctive, but that is not what is happening here.

Italian often uses prendere in places where English uses take, catch, or sometimes get on.

So:

• prendere l’autostrada = to take the motorway / to get on the highway

This is a very normal Italian expression. Similar examples:

• prendere il treno = to take the train
• prendere l’autobus = to take the bus
• prendere la strada per Roma = to take the road to Rome

Because in Italian you usually use the definite article with nouns like this when speaking generally about the motorway/highway you are about to use.

So:

• prendere l’autostrada = to take the motorway

Italian uses articles more often than English does, so even when English might say take the highway or just hit the highway, Italian naturally says prendere l’autostrada.

Yes, both are common, but they are used a little differently.

• auto = car, automobile
• macchina = machine, but very often car in everyday Italian

In many everyday contexts, Italians say:

• la macchina = the car

So you could also say:

• Devo rifornire la macchina di benzina...
• or more naturally in speech: Devo fare benzina...

All are understandable, but auto sounds a bit more neutral/formal than macchina.

Yes, if the context already makes it clear that you mean fuel.

For example:

• Devo rifornire l’auto. = I need to refuel the car.

But di benzina makes the meaning explicit. It can also help distinguish gasoline from other kinds of fuel, such as:

• diesel
• metano
• GPL

They do two different jobs:

1. di benzina
   Here di means something like with/of after rifornire:

   • rifornire l’auto di benzina

2. prima di prendere
   Here di is part of the expression prima di + infinitive:

   • prima di prendere l’autostrada

So even though the same word appears twice, the grammar is different in each case.

The structure is:

• Devo = I have to
• rifornire l’auto di benzina = refuel the car with gasoline
• prima di prendere l’autostrada = before taking the motorway

So the full order is:

[verb] + [object] + [extra detail] + [time clause]

Italian word order here is very similar to natural English word order, which makes this sentence fairly straightforward for English speakers.

Yes, that is grammatical and understandable:

• Devo mettere benzina nell’auto = I need to put gas in the car

However, it sounds a bit more literal. Very common natural options are:

• Devo fare benzina = I need to get gas / fill up
• Devo rifornire l’auto di benzina = I need to refuel the car

So your version works, but fare benzina is often the most colloquial choice.

Usually not in this kind of sentence.

You normally say:

• di benzina
• not della benzina

because benzina is being used as an uncountable substance, like gasoline in English.

You would use an article only in more specific contexts, for example if you mean a particular amount or kind:

• la benzina verde
• della benzina molto costosa

But in this sentence, plain benzina is exactly right.