Q: What type of measurement is the most appropriate for the Cetane Number?
A: Amongst the different ways to determine the Cetane Number, the Cetane Engine (ASTM D 613) is usually the standard.
Q: What is the difference between Cetane Index and Cetane Number?
A: There are 2 ways to determine the Cetane Number of a Diesel Fuel.
The first one, called Calculated Cetane Index, is a theoretical determination. It uses a calculation based on the density and the distillation range of a crude diesel fuel. This estimation is only madeÂ for fuels without any additive in it. The specification of the Cetane Index in Europe is minimum 46.
The second one, called Measured Cetane Number, uses a normalized laboratory test. The Cetane Number is determined by comparing the behavior of the tested fuel to 2 reference mixtures with known Cetane Number. In this case, all fuels, with or without additives, can be tested. The specification in Europe is minimum 51.
Cetane Improver increases the Measured Cetane Number, but has no impact on the Calculated Cetane Index.
Apparatus used for Cetane Number measurement: CFR (Cooperative Fuel Research engine, ASTM D916), IQT (Ignition Quality Tester, D6890), DCN (Derived Cetane Number, ASTM D7170) or CID 510 (Cetane Ignition Delay, ASTM D7668).
Q: Why does the Cetane Index Norm differ from country to country?
A: Each country or state shall define its own diesel specification. For environmental reasons, in year 2000, Europe fixed the Cetane Index at 46, and the Cetane Number at 51, at the same time as low sulfur diesel regulation. Step by step, most of the states around the world would fix the same level of Cetane Number.
In cold weather countries, the Cetane Number can be lower during the winter season. This is explained by the difference in climate, and the addition of kerosen into the diesel. For example: the arctic diesel is at 47-49 in Europe.