Answer :The total calories per serving is different between oil and butter because a tablespoon of oil contain a full tablespoon of fat whereas a tablespoon of butter does not. According to Alice H. Lichtenstein, DSc, director of Tufts HNRCA Cardio – vascular Nutrition Laboratory, butter is about 20% water, by weight; it also contains some milk solids. Vegetable oil, however, is 100% fats, 0% water. A tablespoon of clarified butter (or ghee), which has been heated to evaporate the water and then skimmed to remove milk solids, does indeed contain about 120 calories. Although marginally lower in calories than a tablespoon of vegetable oil, that tablespoon of regular butter also contains 7.3 grams of saturated fat–a good reason to stick with liquid vegetable oils that are lower in this key culprit contributing to unhealthy cholesterol levels.