The basic ratio of oil to vinegar in a vinaigrette is 3:1 - three parts oil to one part vinegar. An example would be 3/4 cup oil to 1/4 cup vinegar. However, it's easy to adjust this you personal tastes. This recipe uses the formula, but then adds a bit of apple cider vinegar to offset the addition of the syrup. When making a quick dinner salad dressing, I will often go with a 2/3 cup oil to 1/3 cup vinegar ratio, so play around with the ratio and see what you like best.