O secador funciona melhor quando eu uso menos condicionador.

Yes. In this sentence, o secador most naturally means the hair dryer.

In Brazilian Portuguese, people often shorten secador de cabelo to just secador when the context is clear.

• secador de cabelo = hair dryer
• secador = dryer / hair dryer, depending on context

So here, o secador funciona melhor means the hair dryer works better.

O is the masculine singular definite article, meaning the.

• o secador = the dryer
• um secador = a dryer

Portuguese uses definite articles more often than English does, so o secador sounds completely natural here.

Because funcionar means to work / to function, and that fits a machine very well.

• O secador funciona melhor = The dryer works better
• O secador é melhor = The dryer is better

These are similar, but not identical:

• funciona melhor focuses on performance or operation
• é melhor is a broader judgment: it is simply better

In this sentence, the idea is that the dryer performs better when less conditioner is used.

Here, melhor means better, and it works like an adverb modifying funciona.

• funciona bem = works well
• funciona melhor = works better

So melhor is describing how the dryer works.

Quando means when, while se means if.

• quando eu uso menos condicionador = when I use less conditioner
• se eu usar menos condicionador = if I use less conditioner

Using quando suggests this is something that actually happens, or something generally true in those situations.

So the sentence means something like: Whenever I use less conditioner, the dryer works better.

If you used se, the sentence would sound more hypothetical.

Yes, it could.

Portuguese often drops subject pronouns when the meaning is clear from the verb ending.

So both are natural:

• quando eu uso menos condicionador
• quando uso menos condicionador

Including eu can add clarity or emphasis, but it is not required here.

Both funciona and uso are in the present indicative:

• funciona = works
• uso = I use

Portuguese, like English, often uses the present tense for general truths, habits, and repeated situations.

So this sentence does not have to mean only right now. It can mean:

• generally
• usually
• whenever this happens

In other words: The dryer works better when I use less conditioner.

Because menos can directly modify a noun.

• menos condicionador = less conditioner
• menos água = less water
• menos açúcar = less sugar

You do not need de here.

Using menos de usually happens in different structures, such as quantities with numbers:

• menos de dez minutos = less than ten minutes

But with a noun like condicionador, menos condicionador is the normal form.

Because Portuguese often leaves out the article when talking about a substance or thing in a general, non-specific way.

• uso menos condicionador = I use less conditioner
• uso menos do condicionador = I use less of the conditioner

The original sentence is general: it does not refer to a specific bottle or specific conditioner already identified in the conversation.

So menos condicionador is the natural choice.

In everyday Brazilian Portuguese, yes, condicionador commonly means hair conditioner, especially in bathroom or hair-care contexts.

If needed, someone could say:

• condicionador de cabelo = hair conditioner

But usually just condicionador is enough.

Yes. A very natural alternative is:

Quando eu uso menos condicionador, o secador funciona melhor.

This means the same thing. The difference is mostly emphasis:

• O secador funciona melhor quando eu uso menos condicionador.
  Starts with the main idea: the dryer works better.

• Quando eu uso menos condicionador, o secador funciona melhor.
  Starts with the condition: when I use less conditioner.

Both are correct and natural.

A rough pronunciation guide:

• o → oo / u sound, often very short
• secador → seh-kah-DOR
• funciona → foon-see-OH-nah
• melhor → meh-LYOR or meh-YOR depending on accent
• quando → KWAN-doo
• eu → something like eh-oo said quickly, often almost yo
• uso → OO-zoo
• menos → MEH-noos
• condicionador → roughly kon-jee-see-o-na-DOR in many Brazilian accents

A couple of useful pronunciation notes:

• Final -r in Brazil is often softer than in English.
• di before i often sounds like jee in many Brazilian accents, which affects condicionador.

Yes, absolutely. That is one of the most natural readings.

Because it uses the present tense plus quando, it often suggests a repeated pattern:

Whenever I use less conditioner, the dryer works better.

So even though the English translation may look simple, the Portuguese sentence can easily express a habit or general observation, not just one moment.