I would recommend using a copper based additive to lower the soot ignition temperature in a particulate trap. Then Look at components with higher heats of combustion.
In mining using a particulate trap is a necessity. You must prevent it from clogging. Using a copper additive will prevent this from happening without a loss of fuel economy. The next improvement can be by increasing the heat of combustion of the fuel. Typical diesel fuel has a heat of combustion around 43 Mj/ kg. There are fuel components that have higher heat of combustion. By increasing the heat of combustion to 47 Mj/ kg you should expect 7 percent improvement in fuel economy and 12% lowering oh THC. These are based on predictions from models using EPA diesel testing.
Lower emissions and increase in fuel economy
Lowering emissions in Diesel engine in mining operations