3 lites of oil is approximately 10 times the recommended calorific input for adult men; it certainly isn't "easy", on the basis of what I've heard from a now-long-deceased acquaintance with cystic fibrosis who was required to consume 10,000 kcal/day just to overcome the medical condition; and 10,000 kcal/day is less than half the amount here (24,436 kcal), which I chose on the basis of it being a lot of fluid to drink in one day even if it was water.