I've been making my own salad dressings lately but I am disappointed with most vinegaretts I've made. I make them with a 3:1 ration of oil to vinegar. I use a good red wine vinegar, a bit of dijon, and some salt and pepper. I find that they are falling a bit flat. I am using DaVinci olive oil.

What I need to know is will I tell a difference if I buy a really good bottle of oil? I don't mind spending $25-$30 on a bottle if I know its worth it, but a little insurance would be nice. Any recommendations?