Wish it were or wish it was?

The truth is that I use them indistinctly...

I take it using 'were' is -always- grammatically correct, whereas using 'was' is technically incorrect or just not acceptable in formal speech, despite the fact that in general it's more common to hear 'I wish it (or she, he) was.'

What do you think?

Hola Flor1990! Tu pregunta me recuerda a una cancion: "I wish you were here". Lo que encontre respecto a tu pregunta fue lo siguiente (espero te ayude sino sigo buscando):
There is often confusion about were (a past subjunctive) and was (a past indicative) after wish. In conditional sentences where the condition is unreal or not yet real and in that clauses after to wish, use were: I wish it were true that he loved me. Were is also used following "as if" and "as though".If the sentence was in the indicative mood, then a sentence would read like this: I wish she was coming to the party. Was has many other uses, e.g., The viewing audience wanted to know if the actress was pregnant. So, the traditional rule requires one to use were rather than was in a contrary-to-fact statement that follows the verb wish. Though many still use this "rule", the indicative was in such clauses can be found almost as often.

Avisame si algo no queda claro! Exitos

Muchas Gracias PIM!

Quedo clarísimo!

In formal written English it is more appropriate to use "I wish it were...". Was is used in everyday colloquial spoken English.

The difference between the use of I wish I were/was remains unclear to me. As far as I could research both ways are acceptable and widely understood. The thing is: Are both grammatically correct? According to traditional grammar books the correct "formal" way would be the use of I wish I were, however more traditional grammar books accept both options.
Not satisfied with these answers I asked an English native friend of mine whether I should use each option. For my surprised she couldn´t give me an answer and told me to use the option I liked the most! LOL

Thank you Gentle!

That's the version I heard the most, although I'd heard what PIM found too!

The question remains, es correcto usar la forma 'wish it was' en textos o essays o cualquier otro tipo de texto formal? O, por ejemplo, si estuvieran completando una evaluación de Inglés y en cierta actividad te pidieran utilizar el subjuntivo, lo pondrían como 'was' o como 'were'? A pesar de que a veces aun los nativos usen 'was' mas comunmente, puede ser que se considere realmente incorrecto en textos formales?

I think most educated people use "were" and I think it is most common but "was" is acceptable. I use "I wish I were". Technically, to say "I wish I was (there, smart, rich, etc)" is like saying "I wish I had been (there, smart, rich, etc.)".

Hace cuanto que no te leia por el foro Vicente!! Gracias por tu aporte!!! Saludos

Muchas gracias por la info Vicente!

Ya medianamente tengo una idea de la diferencia entre estos dos términos!