Box cakes are not necessarily more fluffy than homemade, it all depend on the recipe and the cook how fluffy a homemade cake will be. Box cake mixes are more consistent in many ways, including fluffiness because manufacturers add artificial ingredients that enhance various qualities of the finished cake.
Commercial box cake mixes contain a number of chemical ingredients not found in home kitchens that make the cake very moist and enhance the flavor. For example, a box of Betty Crocker Super Moist Chocolate Fudge Cake Mix includes "Propylene Glycol Mono and Diesters of Fatty Acids, Distilled Monoglycerides, Sodium Stearoyl Lactylate, Dicalcium Phosphate, Cellulose Gum, Xanthan Gum, Artificial Flavor."
It is safe to use Duncan Hines cake mixes for several months after it the best if used by date. The cake will likely bake up flatter than usual however.
Many people prefer the taste of "scratch" cakes. There are certainly far more interesting and creative cake recipes than boxed cake mixes. From a health perspective, cake mixes are full of chemicals, colorings and preservatives, making them imitation food at best.
Yes, cake mixes are made with wheat flour, and all wheat flour contains gluten. Cake mixes contain less gluten than bread mixes or all-purpose flour, but still enough to cause problems for those who are gluten-sensitive. Betty Crocker has a few gluten-free cake mixes on the market, but in general, you'll need to use scratch recipes that use rice flour, or almond meal. If you do a search for "flourless cake recipes," you'll find a few good ones, though they'll be much more dense than what you get with a boxed mix.
There seems to be some misunderstanding. Pillsbury - and other companies - produce chocolate cake mixes, along with chocolate brownie mixes, cookie mixes, and so forth. These mixes include ordinary all purpose or cake flour combined with sugar, cocoa and other ingredients. You use the mix by adding other things, usually eggs, oil or butter, water or milk according to the directions on the package. > But there is not a commercial product that is "chocolate cake flour." Flour is simply flour; cake flour has less gluten (a protein) than all-purpose or bread flour. You need to add cocoa or baking chocolate to the cake flour in order to make chocolate cake.
It will change the consistancy of the cake mix, and also the taste. Olive oil tends to be much thicker and heavier than vegetable or canola oils, which are typically used in cake mixes.
White cake mix cannot be substituted directly for angel food cake mix. The two products have different ingredients that produce different types of cakes. However, if it is only important to have a white cake, and an angel food cake is not specifically required, then you could bake a white cake with a white cake mix instead of trying to make an angel food cake.
Normally a brownie mix does not contain leavening agents, whereas a cake mix does include leavening agents. Also, a typical brownie mix will make much less batter than a cake mix.
Once something has expired (especially after more than a week or two), it is best not to use it anymore.
Then it is NOT cake. (Pie is better than cake)
The egg whites are going to give it more lift.
For water it pretty much is, for substances either denser or fluffier than water it isn't.
Sponge cake is usually lighter than creamed cake is.