is true, 4 litres, no 4 gallon, sorry.But 4 litres I think may be of heavy digestion.
Obviously there is more nutritional value from milk than just whey protein. From my studies you will get a higher amount of whey protein from whole milk, than skim or 1%, but you also get more fat. The benefit over milk than pure whey, from a stand point of putting on mass, is the higher amount of calories in milk. I know a few people who have done this but I never really talked to them about it. I can if you would like.