Not all fats are created equal. So if you're partial to using butter in place of oil in your pancake recipe do it carefully to avoid altering the consistency of the pancakes. Specifically, butter contains less fat than oil, and therefore can solidify, aggressively un-fluffing your delicious pancakes.
If you want to use the same amount of butter as you would oil, you have to clarify it first to remove the milk solids. Place butter in a small saucepan over low heat, stirring occasionally. When you see a white deposit forming on the bottom of your saucepan, remove the pot from the heat and strain the butter into a heat-safe container, discarding the white residue. Congratulations! You've whipped up a batch of ghee.
Alternatively, if you'd rather stick to non-clarified butter, you can find a butter/oil conversion formula to determine the amount you need. For example, if your recipe calls for 1/4 cup of oil, use 1/3 cup of butter. If your recipe calls for 1/2 cup of oil, use 2/3 cup of butter.
Keep in mind that butter browns more quickly so check your pancakes more frequently to avoid burning them.
If you're looking to decrease the fat content in your pancakes, you can substitute an equal measure of applesauce for the oil. This can also work in many other recipes, including cakes and muffins.