I have been a process operator in a oil refinery for 35 years. Like others have said there is NOT good and bad Diesel, only different additive packages. We can and do change the blends of Diesel to meet the customers specific specs. Like No 1 or 2 Diesels, Cetane Indexes (kinda like octane) etc..
Additives that can be added for customers are Detergents, Lubricity, Stabilizers, Cetane Improvers, Pour Point reducers (this helps in cold weather), biocides, and corrosion inhibitors.
Fun Fact, Kerosene is Jet Fuel. Its Distillation numbers are very close to Diesel, the Refiner will adjust the Freeze Point of the Jet Fuel for obvious reasons
In the Refinery I work at every drop of Kerosene is blended into the Diesel pool cause that's where the economics point (more money).
Another thing, there are strict standards set by the API and ASTM for Hydrocarbon Fuels, so nobody gets to cheat the customer.