In the first chapter Nick exclaims to the readers, "I'm inclined to reserve all judgements" in this statement Nick is trying to set him set up to the readers that he is reliable narrator (Fitzgerald 1) He is trying to portray that all he says is the truth. As the reader, at the end of chapter 1 it is evident that this is not exactly the truth when he says that Daisy should leave Tom. In this instance Nick is making a judgement and going against what he said.
In another instance readers can see one again that Nick is an unreliable narrator when he states, "I have been drunk twice in my life and the second time was that afternoon" when Nick says that afternoons he is referring to the party the party at Tom and Myrtles apartment in New York City (Fitzgerald 29). Nick does not quite remember all of the details from that day, all of the details come a little hazy to Nick. Readers do not exactly know the true event that had happened in chapter two because Nick is being portrayed as an unreliable narrator.
In chapter eight Nick has advice that we wants to give to Gatsby. Nick believes that Gatsby should leave town so that he will not be charged for the murder of Myrtle. This is in fact showing that Nick is a reliable narrator when he says this, but Nick never actually gave this advice to Gatsby. Readers know this when Nick says, "he was clutching at the last hope and I couldn't bear to shake him free" he did not have the guts to tell this to Gatsby (Fitzgerald 148). Nick did not want to hurt his friend Gatsby, but in reality the truth hurts. If Nick was a reliable narrator he would of risk hurting Gatsby's feeling and telling him this.