What is d2?
D2 is the second distillate from the crude, and can be used without reformers and additives. The first engines used D2 as fuel - before petrol cars as we know them today were invented. That is because the engine invented by a German called Diesel, requires no spark plugs. The diesel engine will ignite and combust when the pressure increases so that the heated "plug" makes it explode. Here we get the name "Diesel" - since the same principles are used in diesel engines today. However, automotive diesel that you fill has additives that the refinery will add to make the engine more efficient and also easier to start in the winter. if you read the small print, you will see that diesel changes "flash point" in the winter. It also has additives to absorb water that condense as you have it in your car (same as petrol) - but since the diesel is injected right into the cylinder, the ice will destroy the nozzles long before the engine. If you use summer diesel in the winter, you will get better mileage, but your fuel pipes may freeze and can also burst, and the wax makes the diesel flow thicker.
D2 is also known as Gasoil. The principal differentiators in GASOIL or D2 is the content of sulphur. Just 10 years ago, the US EPA introduced a limit of 4% sulphur in the GASOIL, whereas Europe and the rest of the world followed later. As in most other cases, when you first have to remove the sulphur, it was soon discovered ways of doing this more efficient. Then it was discovered that the sulphur, as sulphuric acid, could be traded with a good profit - which now is the motivator for extracting as much as possible. Well, pour this over limestone, and you get cement and add to it other chemicals, and you can get cement that are more valuable than the Gasoil. So "Low Sulphur Gasoil" is no longer 4 percent - but below 0.2 percent. Then we have a new, "Ultra Low Sulphur" at 0.02% at the most, and the limit here is (a) that mass spectographs requires extensive calibration to measure below 1000ppm, and (b) sulphur has a way to form clogs - the molecules binds to free hydrogen molecules and form a cluster of molecules that will break if "cracked" by the refinery, but as explained above, D2 is a distillate and has not been "cracked". So - take a pint of ULSG, you may have the misfortune of having 0.1 percent sulphur - but the average for a barrel will be less then 0.02 - its just you managed to get a cluster of molecules.
The International Standardisation Organisation - ISO has a standard for D2 that most oil companies use as their reference.
However, in the US, it is ANSI that has defined the US national standard for D2, according to proposals from the ASTM, API and EPA.
In Europe, similar national variants exists, e.g. in Germany set by DIN, and in Russia by GOST.
The GOST variant for D2/Gasoil is GOST 305-82 and specifies now a sulphur content of 0.02 MAX which is according to the ISO standard. However, the ANSI standard will call this "Ultra Low Sulphur", and retain 0,2% (2000ppm) as the "Low sulphur. The reduction of sulphur in the Gasoil used for heating has contributed to less pollution in many cities.
Automotive diesel has national variants - but the usual variants traded is EN590 and EN560 which are specified by ISO in Paris. These qualities may be sold in the US, and be compliant with EPA regulations in the US. Because of the way Diesel invented his engine, the engine is very flexible and adjust to the small differences. Automotive diesel is now tested in planes with great success, where you get greater mileage per weight unit of fuel - as much as 40% increase. In these days, when no stone remains unturned to reduce emissions, one outcome may be that planes will fly on Gasoil and not kerosene. The problem is condensate / ice particles and wax that may cause the jet engine (which is a turbine) to be completely destroyed. A preliminary solution is to heat the gasoil before injection, and pass it through a electrostatic filter. Come up with a simpler solution, and you can become a millionaire.