É importante que você não use muito óleo para fritar o peixe.

Because this sentence uses the present subjunctive.

After expressions like É importante que..., Portuguese usually requires the subjunctive, because the speaker is expressing:

• importance
• necessity
• recommendation
• doubt
• emotion
• possibility

So:

• você usa = indicative, used for facts or habits
• você use = subjunctive, used here after É importante que...

Examples:

• É importante que você estude.
• É bom que ele chegue cedo.
• É necessário que nós façamos isso.

So que você não use means that you not use / that you don’t use in the sense of a recommendation or requirement.

In Portuguese, não normally goes directly before the verb it negates.

So:

• você não use muito óleo = you not use too much oil

That is the standard position in a sentence like this.

Compare:

• Eu não sei. = I don’t know.
• Ela não quer sair. = She doesn’t want to leave.
• É importante que você não use muito óleo.

Both are possible, but they feel a little different.

• É importante que você não use muito óleo... = It is important that you not use too much oil...
• Você não deve usar muito óleo... = You shouldn’t use too much oil...

The version with É importante que... sounds a bit more indirect and explanatory. It focuses on the importance of the action.
The version with não deve sounds more like direct advice or instruction.

So the original sentence is natural if the speaker wants to sound informative or careful rather than commanding.

Because óleo is an uncountable noun here, like oil in English.

When muito means a lot of / much, it stays singular with uncountable nouns:

• muito óleo = a lot of oil / too much oil
• muita água = a lot of water
• muito tempo = a lot of time

With countable plural nouns, it changes:

• muitos livros = many books
• muitas pessoas = many people

So muito óleo is correct because oil is being treated as a substance, not as countable individual units.

Portuguese often leaves out the article when speaking about a substance in a general amount.

So:

• usar muito óleo = to use a lot of oil

This is natural because the sentence is not referring to a specific oil already identified in the conversation. It just means oil in general.

You could sometimes hear muito do óleo or o óleo in other contexts, but here that would change the meaning and sound less natural.

It expresses purpose: for frying the fish / to fry the fish.

In Portuguese, para + infinitive is very common for showing purpose.

Examples:

• Estudo para aprender. = I study to learn.
• Comprei óleo para fritar batata. = I bought oil to fry potatoes.
• É importante que você não use muito óleo para fritar o peixe.

So here it explains what the oil is being used for.

Both can exist, but fritar o peixe is more specific.

• fritar o peixe = fry the fish, a specific fish or the fish being discussed
• fritar peixe = fry fish, more general

Portuguese often uses the definite article more than English does, especially when referring to something specific or understood from context.

So in a cooking situation, o peixe may refer to the fish being prepared right now.

Yes, it can be omitted, because the verb form already helps show the subject in context.

So you could say:

• É importante que não use muito óleo para fritar o peixe.

However, keeping você is very common in Brazilian Portuguese, especially in speech, because it makes the sentence clearer and more natural in many regions.

So:

• com você = a bit clearer, often more conversational
• without você = also grammatical, sometimes slightly more compact

It is fairly neutral and natural. It is not extremely formal, and it is not slangy either.

Why?

• você is the normal everyday you in most of Brazil.
• É importante que... is common in both spoken and written Portuguese.
• The vocabulary is standard and neutral.

So this sentence works well in:

• conversation
• instructions
• advice
• recipes
• health or cooking explanations

Yes. In Brazilian Portuguese, that version is also very common and natural:

• É importante que você não use muito óleo...
• É importante você não usar muito óleo...

The difference is mainly grammatical style:

1. É importante que você não use...

   • uses que + subjunctive
   • often feels a bit more traditional or explicitly grammatical

2. É importante você não usar...

   • uses a structure with the infinitive
   • very common in everyday Brazilian Portuguese

Both are correct. The original sentence is a good textbook example because it clearly shows the subjunctive pattern.

Use is the present subjunctive form of usar for eu, você/ele/ela, and o senhor/a senhora.

Here is the present subjunctive of usar:

• que eu use
• que você use
• que ele/ela use
• que nós usemos
• que vocês usem
• que eles/elas usem

So in the sentence:

• que você não use = that you not use

This is why it looks different from the indicative:

• você usa = you use
• que você use = that you use

They are similar, but not exactly the same in tone.

• muito óleo = a lot of oil / too much oil, depending on context
• óleo demais = too much oil / oil in excess

In this sentence:

• não use muito óleo sounds very natural and neutral
• não use óleo demais also works, but it emphasizes excess a little more directly

Examples:

• Não coloque muito sal. = Don’t add too much salt.
• Não coloque sal demais. = Don’t add too much salt.

Both are common, but muito óleo fits the sentence very smoothly.

The original sentence is already natural, but in everyday speech Brazilians might also say:

• É importante você não usar muito óleo pra fritar o peixe.
• Não é bom usar muito óleo pra fritar o peixe.
• Melhor não usar muito óleo pra fritar o peixe.

The biggest spoken change is often:

• para → pra

So:

• para fritar = more careful/neutral pronunciation
• pra fritar = very common in speech

The original version is excellent for learning and completely natural in standard Portuguese.