Learn Hardcore Portuguese (Portugal): Se o salário for maior, nós vamos poupar mais dinheiro. - If the salary is higher, we are going to save more money.

Because for here is the future subjunctive of ser, and after se (when you are talking about a future or hypothetical situation), Portuguese normally uses the future subjunctive, not the present indicative.

Se o salário for maior…
= If the salary is higher (in the future / in that situation)

Using é (Se o salário é maior…) sounds like you are talking about something that is already known to be true as a general fact, not a future or hypothetical possibility.

What tense exactly is for, and how is ser conjugated in that tense?

For is the future subjunctive of ser.

Future subjunctive of ser:

se eu for
se tu fores
se ele / ela / você for
se nós formos
se vós fordes
se eles / elas / vocês forem

You mostly see this tense after conjunctions like se, quando, assim que, enquanto, when they refer to the future:

Se ele for ao banco, liga-me.
If he goes to the bank, call me.
Quando fores a Lisboa, visita-me.
When you go to Lisbon, visit me.

In your sentence, o salário is 3rd person singular, so you use for.

Could I say Se o salário é maior, nós vamos poupar mais dinheiro instead?

You can, but it changes the nuance.

Se o salário for maior, nós vamos poupar mais dinheiro.
→ Hypothetical / future condition: If the (next / future) salary turns out to be higher, then we will save more money.
Se o salário é maior, nós vamos poupar mais dinheiro.
→ Sounds more like a general rule or fact: Whenever the salary is higher, we save more money.
(Similar to: If the salary is higher, we save more money as a timeless rule.)

For a specific future possibility (e.g. a raise you might get), Se o salário for maior… is the natural choice.

Why does Portuguese use a different tense from English? English says “If the salary is higher…” with the present.

English often uses the present indicative in the if-clause for future meaning:

If the salary is higher, we will save more money.

Portuguese often uses the future subjunctive in this kind of future condition:

Se o salário for maior, nós vamos poupar mais dinheiro.

So, even though English has is, Portuguese prefers for in this future context. It is a structural difference between the two languages; you cannot translate the tense directly here.

Can I say Se o salário será maior or Se o salário seria maior?

No, those are not idiomatic in this context.

In Portuguese, you do not normally use the future indicative or conditional directly after se to express a condition:

✗ Se o salário será maior… (incorrect / unnatural)
✗ Se o salário seria maior… (incorrect / unnatural)

You use:

se
- present indicative (é) for a factual / general condition
se
- future subjunctive (for) for a specific future/hypothetical condition

So the natural choices are:

Se o salário é maior, nós poupamos mais dinheiro. (general rule)
Se o salário for maior, nós vamos poupar mais dinheiro. (future possibility)

Why is it nós vamos poupar instead of just a future tense like pouparemos?

Portuguese has two common ways to talk about the future:

Ir (present) + infinitive
- nós vamos poupar
  (we are going to save / we will save)
Simple future attached to the verb
- pouparemos

Both are grammatically correct here:

Se o salário for maior, nós vamos poupar mais dinheiro.
Se o salário for maior, pouparemos mais dinheiro.

In everyday European Portuguese, ir + infinitive (vamos poupar) is much more common in speech. Pouparemos sounds more formal or written.

Is it necessary to say nós, or can I just say Vamos poupar mais dinheiro?

You can absolutely drop nós:

Se o salário for maior, vamos poupar mais dinheiro.

Portuguese is a pro-drop language: the verb ending already tells you the subject, so the pronoun is often omitted.

Including nós can:

give slight emphasis (we, as opposed to someone else), or
make the subject extra clear in complex contexts.

In a simple sentence like this, both versions are natural.

Why is maior used here, and not something like mais alto?

Maior is the comparative form of grande and is very commonly used for quantities and amounts, including money and salaries:

um salário maior = a higher / bigger salary
mais dinheiro = more money

You could say um salário mais alto, but for money, maior is more common and sounds more natural in European Portuguese.

So:

Se o salário for maior… = If the salary is higher…
Se o salário for mais alto… = possible, but less idiomatic for salary.

What is the difference between poupar, guardar, and economizar when talking about saving money?

All can relate to the idea of saving, but they have different typical uses, especially in European Portuguese:

poupar
Main everyday verb for saving money by not spending it.
- Quero poupar dinheiro. – I want to save money.
- Estamos a poupar para comprar uma casa.
guardar
Means to keep / put aside / store.
With money, it can mean putting it aside (physically or mentally), but it focuses on keeping, not necessarily on the idea of being economical.
- Guardei algum dinheiro de lado.
economizar
Exists in European Portuguese but is less frequent in speech; it's more formal, and is very common in Brazilian Portuguese.
- Temos de economizar energia / água.

In your sentence, in European Portuguese, poupar mais dinheiro is the most natural choice.

Can I leave out dinheiro and just say vamos poupar mais?

Yes, if the context already makes it clear that you are talking about money, you can simply say:

Se o salário for maior, vamos poupar mais.

Mais then means more (of it), and dinheiro is understood from context. Both versions are correct; including dinheiro just makes it explicit.

Is salário masculine, and are there any common alternatives?

Yes, salário is masculine, so you say:

o salário
um salário
os salários

A very common synonym in European Portuguese is ordenado (also masculine):

o ordenado
um ordenado melhor = a better salary

In many contexts, salário and ordenado are interchangeable:

Se o ordenado for maior, vamos poupar mais dinheiro.

Can I change the word order and put the se-clause at the end?

Yes. Both orders are correct:

Se o salário for maior, nós vamos poupar mais dinheiro.
Nós vamos poupar mais dinheiro se o salário for maior.

About the comma:

When the se-clause comes first, you normally use a comma:
Se o salário for maior, vamos poupar mais dinheiro.
When it comes after, you usually do not use a comma:
Vamos poupar mais dinheiro se o salário for maior.

This mirrors English quite closely:
If the salary is higher, we will save more money / We will save more money if the salary is higher.

Why is it mais dinheiro and not dinheiro mais?

In Portuguese, quantifiers like mais, menos, muito, pouco, algum normally come before the noun:

mais dinheiro – more money
menos tempo – less time
muito trabalho – a lot of work

Adjectives usually come after the noun (though there are many exceptions), but mais here is not an adjective; it is a quantifier (meaning more). So:

mais dinheiro is the normal order
✗ dinheiro mais would be wrong in this meaning.