Por más que use blanqueador, la mancha no sale.

Here por más que introduces a concessive idea: something is true despite another effort or circumstance.

In sentences like this, it often means:

• no matter how much
• however much
• sometimes even though, depending on context

So the structure is roughly:

por más que + verb, result that still does not change.

The idea is: using bleach does not solve the problem, no matter how much of it is used.

Use is the present subjunctive form of usar for yo.

This is common after por más que when Spanish presents the action as an attempt, possibility, or something that does not affect the outcome. The sentence is not just reporting a neutral fact; it is stressing that the result stays the same regardless of the effort.

• yo uso = present indicative
• yo use = present subjunctive

So por más que use blanqueador has the sense of no matter how much I use bleach.

You may also hear por más que uso... in some contexts, but por más que use... is very natural and standard for this kind of idea.

Because Spanish often drops subject pronouns when the verb ending already shows who the subject is.

Here, use tells you the subject is yo.

So:

• Por más que use blanqueador... = natural
• Por más que yo use blanqueador... = also correct, but more emphatic

Adding yo would usually sound like you are stressing I, perhaps in contrast with someone else.

Blanqueador usually means a bleaching product or whitener, often what English speakers would simply call bleach in household context.

Depending on the country, people might also say:

• cloro
• lavandina
• lejía (more associated with Spain)

So blanqueador is a good general word, but the most common everyday term can vary by region.

Yes, salir often means to go out / to come out / to leave, but in cleaning and laundry contexts it has a very common extended meaning:

• La mancha sale = the stain comes out
• La tinta no sale = the ink does not come out

In English, we also say a stain comes out, so the logic is actually pretty similar. Spanish uses salir very naturally for something being removed from fabric or a surface.

The subject is la mancha.

So grammatically, the sentence says:

• la mancha = the stain
• sale = comes out

That is why the verb is sale and not salen:

• la mancha sale
• las manchas salen

Even though English often focuses on the person removing the stain, Spanish here is focusing on the stain itself as the thing that either comes out or does not.

Both are correct and natural, but they are slightly different in feel.

• La mancha no sale = the stain won’t come out
• La mancha no se quita = the stain won’t come off / can’t be removed

In everyday speech, no sale is very common for stains, especially with clothing, fabric, or spots caused by food, ink, grease, etc.

No se quita is also very common and may sound a bit more directly focused on removal.

So this sentence sounds very natural, not unusual.

Yes. Por mucho que is also correct and very close in meaning.

Both can express:

• no matter how much
• however much

In many cases, por más que and por mucho que are interchangeable.

That said, por más que is extremely common in this concessive pattern and sounds very natural here.

Because Spanish usually uses the definite article when talking about a specific, known thing.

Here, la mancha means the stain—the particular stain the speaker is dealing with.

Saying just mancha would sound incomplete in this sentence.

It most naturally suggests a current or repeated situation: the speaker has tried bleach, possibly more than once, and the stain still does not come out.

The present tense supports that kind of meaning in Spanish:

• use in the subordinate clause
• no sale in the main clause

If you wanted to place it clearly in the past, Spanish would normally change the tenses:

• Por más que usé blanqueador, la mancha no salió
• Por más que usara blanqueador, la mancha no salía

So the original sentence sounds like a present, ongoing frustration.