when somebody asks you whether you know something or not, or what's your opinion about something, you say that you know little about it and you are not interested in this thing, you could say I was just passing by.So you could say 我只是来打酱油的.

Yeah, it's means "It's none of my busyness", but there isn't any emotional feelings in it.

This is interesting because the phrase "Its none of my business" in English is used in an entirely different context.

I've spoke with my teacher and I think the translation falls into one of two American colloquisms: 1) I don't have a dog in this fight. 2) I really don't have an opinion (a thought on the subject).

打酱油， 是代表 none of my business, 但是语气非常缓和。 其实这句话毫无意义， 一般用来在论坛发帖的时候， 为了争论坛的积分， 但是确实又没有任何评论发表的时候， 就说自己 打酱油的飘过。