O filtro de óleo está sujo.

O means the. Portuguese often uses definite articles more regularly than English does, so o filtro is simply the filter.

• o = the for a masculine singular noun
• filtro = filter

So o filtro = the filter.

If you said just filtro, it would sound more like filter or a filter, depending on context, but in this sentence the specific article o is the natural choice.

De usually means of or from, and here it works like of in English:

• filtro de óleo = oil filter
• literally: filter of oil

This noun + de + noun pattern is very common in Portuguese:

• copo de água = glass of water
• máquina de lavar = washing machine
• sapato de couro = leather shoe

So filtro de óleo is the normal Portuguese way to say oil filter.

The accent in óleo shows both stress and pronunciation.

• It tells you the stressed syllable is ó
• It also helps show that the word is pronounced roughly as OH-lee-oh

Without the accent, the pronunciation rules would suggest something different. In Portuguese, accent marks are important because they often tell you exactly where the stress goes.

Portuguese has two main verbs for to be: ser and estar.

Here, está is used because dirty is seen as a condition or state, not a permanent characteristic.

• está sujo = is dirty / is in a dirty state
• é is more for identity, essential characteristics, or permanent descriptions

So for things like:

• The floor is wet
• The shirt is clean
• The filter is dirty

Portuguese normally uses estar.

Está is the third-person singular form of estar in the present tense.

Conjugation of estar in the present:

• eu estou = I am
• você / ele / ela está = you are / he is / she is
• nós estamos = we are
• vocês / eles / elas estão = you are / they are

Since o filtro is a singular thing, Portuguese uses está.

Because sujo has to agree with filtro, and filtro is a masculine singular noun.

Agreement pattern:

• sujo = masculine singular
• suja = feminine singular
• sujos = masculine plural
• sujas = feminine plural

Examples:

• O filtro está sujo. = The filter is dirty.
• A camisa está suja. = The shirt is dirty.
• Os filtros estão sujos. = The filters are dirty.

You usually learn the gender of the noun together with the article:

• o filtro = masculine
• a would mark a feminine noun

A lot of Portuguese nouns ending in -o are masculine, though not all. In this sentence, the article o clearly shows that filtro is masculine.

That is why the adjective also appears as sujo.

In Portuguese, adjectives often come after the noun, especially in straightforward descriptive sentences.

So:

• filtro sujo = dirty filter
• o filtro está sujo = the filter is dirty

This is very normal word order in Portuguese. Some adjectives can come before the noun, but in a basic sentence like this, sujo after the noun or after the verb is exactly what you would expect.

Yes. Sujo literally means dirty, but like English dirty, it can also be used more broadly depending on context.

Possible meanings include:

• physically dirty
• contaminated
• figuratively dirty in a moral or improper sense

In O filtro de óleo está sujo, the most natural meaning is the literal one: the oil filter is dirty.

A simple approximate pronunciation for an English speaker is:

oo FEEL-troo djee OH-lee-oh es-TAH SOO-zhoo

A few notes for Brazilian Portuguese pronunciation:

• o at the beginning of o often sounds like oo
• de before a vowel can sound like djee in many Brazilian accents
• está is stressed on the last syllable: es-TAH
• j in sujo sounds like the s in measure

A more natural connected pronunciation may sound something like:

u FEEL-tru dji OH-lee-u es-TAH SU-zhu

The plural would be:

Os filtros de óleo estão sujos. = The oil filters are dirty.

Notice all the changes:

• o → os
• filtro → filtros
• está → estão
• sujo → sujos

This shows how Portuguese marks plurality in several parts of the sentence.

Grammatically, people would understand it, but it is usually not the best choice here.

• está sujo = it is dirty right now / it is in a dirty condition
• é sujo = it is dirty by nature / it is generally a dirty thing

Since an oil filter is not inherently dirty all the time, está sujo is the natural version.

Yes, if the context already makes it clear what filter you mean.

• O filtro está sujo. = The filter is dirty.
• O filtro de óleo está sujo. = The oil filter is dirty.

Adding de óleo makes it more specific. If you are talking about a car and there could be several filters, including de óleo helps avoid ambiguity.