Whole eggs will not give you the same effect as mayonnaise. The egg white-portion will actually âdry-outâ the cake.
âFatâ content is one of the key variables in making a moist cake (fyi-sugar is the other key cake âmoistenerâ). You add âfatâ by adding one or more of the following (butter, sour cream, oil, egg yolks, etc.) or even a âfat-substituteâ like applesauce.
The combination of egg yolks and oil works really well. The lecithin (a powerful emulsifier) in the egg yolks helps distribute and suspend the oil. Egg yolks are also a significant source of fat.
It all depends upon what taste and mouthfeel you want to achieve.