D2 is a refinery abbreviation for Gasoil. It is the second distillate from the crude and can be, used without reformers and additives. Therefore, 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 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 condenses 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.
The principal differentiator in GASOIL or D2 is the content of sulfur. Just 10 years ago, the US EPA introduced a limit of 4% sulfur 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 sulfur, it was soon discovered ways of doing this are, more efficient. Then it was, discovered that the sulfur, 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 is more valuable than the Gasoil / D2.
So “Low sulfur 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 spectrographs require extensive calibration to measure below 1000ppm, and (b) sulfur has a way to form clogs – the molecules bind 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 sulfur – but the average for a barrel will be less than 0.02 – it is just you managed to get a cluster of molecules.
