There are two common methods for measuring cetane rating in diesel fuel:

The cetane number is measured using a specific test engine, and will give the best approximation as to how it will perform in the real world.

The cetane index is a calculation based on the fuel's properties, which is an estimate of the cetane number. This method can't take into account the various additives used in the final product, so the CI will be a few points lower than the true CN.



Australian automotive diesel specifies a CI of 46 (as does EN590). This will naturally mean a CN range of 48-52, so even if Australia doesn't specify a CN of 51, I would expect in most cases that the final product should have a CN of 49-51 when it reaches the service station, so IMO that in itself is not enough of a concern.

In any case, the significant reduction of sulphur content in fuel will have had by far the biggest effect on smoke and particulate matter reduction, rather than any change in CN.

As far as the product leaving the refinery is concerned, our diesel standard is closely aligned with Europe, as nearly every parameter is identical to EN590 (although depending on the region or circumstance, there may be case for using fuel additives as the product moves down the supply chain).

My main message is that there's nothing wrong with using fuel additives, but just remain vigilant (and use common sense) about what one pours in the vehicle's fuel tank.