Biodiesel has promising lubricating properties and cetane ratings compared to low sulfur diesel fuels. It is used as a diesel cetane improver. Hence, higher speed diesel engines operate more effectively with higher cetane number fuels. The biodiesel made from mustard oil has good flow properties and cetane ratings. The principal measure of diesel fuel quality is its cetane number. California diesel fuel has a minimum cetane of 53. The fuel contains no sulfur or aromatics, and has a high cetane number. A cetane number is a measure of the delay of ignition of a diesel fuel. Premium diesel fuel can have a cetane number as high as 60. Neste MY Renewable Diesel sold in Finland has a minimum cetane number of 70. Diesel fuels are characterised by their cetane number, cetane being an older name for hexadecane. Premium diesels may or may not have higher cetane, depending on the supplier. Diesel fuels are characterized by their cetane number, cetane being an old name for hexadecane. Audi has co-developed E-diesel, a carbon-neutral fuel with a high cetane number. European (EN 590 standard) road diesel has a minimum cetane number of 51.