Do you taste the food when you cook? This should be done every time: you can fool the eye, but the taste cannot be deceived. If there is a mistake, you may still have time to correct it. The proportion of 3 parts vegetable oil to 1 part vinegar for vinaigrette is not a rock, but just a guideline. The main thing is to achieve the right balance of acidity, saltiness, and sweetness: this question will be answered by your taste. The best way to taste the dressing is to dip a leaf of lettuce into it, shake off the excess, and chew. It's better than tasting it in a ready-made salad. Beat the vinaigrette with a blender or a whisk, and if neither one of them is at hand, pour it into a bottle, close the lid, and shake well.