Learn Spanish (Latin America): De lubricar el motor, ellos usarán un aceite nuevo. - If lubricating the motor, they will use a new oil.

In Spanish, using de followed by an infinitive is a concise way to form a conditional "if" clause. Here, de lubricar means the exact same thing as si lubrican (if they lubricate). You will often see this structure in formal speech, technical manuals, or written instructions.

How do we know who is doing the lubricating if lubricar is an infinitive?

When you use the de + infinitive structure, the person performing the action is usually assumed to be the subject of the main clause. Since the main clause says ellos usarán (they will use), we know that ellos are also the ones who might lubricate the motor.

Why does the main clause use the future tense (usarán)?

The de + simple infinitive structure sets up a real or likely condition, just like a standard "if" clause in the present tense. Because it is a realistic possibility, the result is what will actually happen, so we use the future tense usarán. If this were a highly unlikely hypothetical scenario, the main clause would use the conditional tense (usarían).

Does nuevo change its meaning depending on whether it comes before or after aceite?