Favor de / Por favor/ Conditional
Which is the most polite?
When should each be used?
- Sr. Mendez, favor de cerrar la ventana.
- Sr. Mendez, ¿Podrías cerrar la ventana?
- Sr. Mendez, por favor, cierre Ud. la ventana.
Could the perterite imperfect, subjunctive mood be used? Sr. Mendez, ¿Pudieras cerrar la ventana?
Yes, you can, but it is rarely used (except in a few regions). There are only three verbs that can be used for probability or politeness in imperfect subjunctive instead of the conditional: querer is used everywhere quite often, deber is used much less frequently, but it is still in use, but poder is almost not used at all in many places, and to some native speakers it even sounds wrong.
Anyway, I guess that if imperfect subjunctive is a tense, and it can replace the conditional, then it is fair to conclude that the latter must also be a tense (in Spanish), and not a mood, right?
Could the perterite imperfect, subjunctive mood be used?
Sr. Mendez, ¿Pudieras cerrar la ventana'
I agree with James.
"Favor de cerrar la ventana" is too colloquial in Spain, and it can even be regarded as rude (in many parts of America is fine, though). Notice that it is an order anyway, and not a request, so it can not be too polite. It is a short for "(Haga el) favor de cerrar la ventana", which is a much more polite sentence everywhere.
"Cierre usted la ventana" is reasonably polite, but unless you add "por favor", a question is often more polite. "Haga el favor de..." is a bit more polite.
"¿Podrías cerrar la ventana'" is fine in Spain, but not formal. "¿Podría...'" would make the sentence more polite (in Spain), by using "usted".
"¿Sería tan amable de...'" is very polite, and much more formal.
Going to extremes, you could opt for:
¿Tendría la amabilidad de...'
I'll let a native speaker give you the order (if possible), but another very polite construction is this:
Sr. Mendez, ¿sería tan amable de cerrar(me) la ventana'