What ingredient makes a moister lighter cake?

Using oil instead of butter in a cake recipe will result in a moister, lighter cake. This is because oil is a liquid at room temperature, while butter is a solid. When you cream butter and sugar together, you are creating air pockets in the mixture. These air pockets are what give cake its light and fluffy texture. When you use oil instead of butter, the oil simply coats the flour and sugar, preventing the formation of air pockets. This results in a denser, heavier cake.