There are already ones that run on wood, vegetable oil, sunshine, and water---Isn't that an even cheaper alternative?
Milk prices are relative to the price of diesel, you really wouldn't save much, besides milk is primarily water.
Great idea. Then if you wanted premium premium, you could get "mustle milk" with protein, unleaded supreme would be "heavy cream" and regular would be two percent fat...Why didn't "drive" think of that be "Ford".