what is the difference on using oil or butter in a cake?
Cakes made with oil tend to be softer and more moist than cakes made with butter. Also oil based cakes that are refrigerated do not harden like butter cakes. For the latter ones it is usually best to wait until they get to room temperature so as to soften up the crumb. Butter based cakes tend to be a bit more flavorful. So if you have
a plain vanilla oil based cake and a plain vanilla butter based cake, the former may have a softer texture but the latter may be more flavorful. That is why chiffon cakes which are oil based often call for more vanilla extract,
citrus zest etc. to enhance flavor.
Butter has cholesterol. Oil doesn't. Both are loaded with fat. If you want your cake to feel less guilty but taste just as good, try substituting applesauce.
Oil has an open spongy texture, like a boxed cake mix and is very moist. I think butter based cakes have a softer more close knit crumb. Usually for butter cakes you will begin by creaming the butter with the sugar, add eggs one at a time, then the dry alternating with a liquid, like milk. For oil based cakes you measure the wet and dry ingredients in separate bowls and combine so they can be put together quickly.
oil based cakes actually have a tighter crumb unless it's a sponge cake (like chiffon) that is leavened by egg whites.That is because oil cakes are chemically leavened with baking powder or soda. They are also very moist. Butter based cakes get their leavening from whipping tiny air bubbles into it when using the creaming method by mixing sugar and butter as well as baking powder or baking soda so they will be a bit airier, but still dense. Also in regards to apple sauce for butter, it will probably make the cake dense and not as tender. Try substituting bananas if your really that concerned with it. Or half of the butter with a fruit puree or a fruit butter (like apple butter) It is important to remember substituting fats and eggs out for plant products will change the results of the cake so plan wisely.