In the 1960s, the US Army did a study of fuel storage life. They found that diesel fuels could be stored for 10 years or more without a problem.
Today, it’s not even close. Diesel Fuel #2 degrades 26% in the first 28 days and may be up to 95% if it has water in it. So, fuel storage life is way, way down.
So, what changed? Simply put, refineries are under pressure to produce more fuel from the same amount of crude, in order to meet ever-growing demand, they’ve had to develop new processes and methods to maximize that yield – processes like hydrocracking. In a nutshell, they break the larger molecules in crude oil into smaller molecules that can be turned into fuels like gasoline and diesel. So, they get more diesel fuel and gasoline from each barrel of crude oil.