As an educated, native-speaker of English I am fairly well versed in the language. Occasionally, there will be a rule I have forgotten or perhaps never properly learned. This brings me to the rule I reinforced today.
Can you use the phrases "If I was" and "If I were" interchangeably? Isn't "If I were" grammatically incorrect since the verb form "were" is supposed to be paired with plural nouns? The answers are no these phrases should not be used interchangeably and both are grammatically correct depending on the context. There is a difference between these two phrases. It is interesting in all my years of learning English grammar I never learned about subjunctive mood until I started learning a foreign language (Spanish).
The subjunctive mood is used to express a wish, a command, or something contrary to fact. The phrase "If I were" is subjunctive mood. The phrase "I was" is indicative mood based in fact.
Here are some examples:
If I were Superman, I could fly around and avoid all this traffic, but I would experience greater exposure to airborne carcinogens. Obviously I cannot be Superman.
If I was mean to you, I apologize. Maybe I was mean. It is in the realm of possibility.
If I were you, I would not grab that barbed-wire piece of fence attached to that bucket full of razor blades placed precariously on the edge of the barn located behind you. But I'm not you.
If I was asleep, I would have already put my phone in airplane mode to eliminate interruptions and reduce EMF exposure. Again, realm of possibility.
Most people stick with one phrase or the other, but there is a subtle difference for the sticklers out there.