The effectiveness of cetane-improvement additives tends to be linear with addition rate;
however, the improvement can vary with different blendstocks and in particular with hydrocarbon type.
Paraffins, which already have a high cetane number, respond best to additives;
and aromatics, which have a lower intrinsic cetane value, have a poorer response.
In practice, 500 ppm of the standard alkyl nitrate can increase the cetane number of typical diesel fuels by about 2 to 5 numbers.
The cost of additives needed to increase a diesel blend by 5 cetane numbers is about $0.50 per barrel.
However, because peroxides increase the rate of gum, varnish and sediment formation in borderline unstable fuels, they have been used only in extremely stable fuels.
With your high quality diesel fuel, the effect will be even better than with the crud sold as diesel here in North America.