Not in the oil.
Modern crankcase oils come with an additive package that is precisely developed. Introducing another additive disturbs that package and can even be detrimental. The simple truth is that the best practice for crankcase oil is to change it and keep it clean. Also, diesel engines require oil that is rated for diesels and not just for gasoline engines. That rating is clearly indicated on the bottle, usually in several places. You should be familiar with both the viscosity and API rating that is required for your engine.
Modern crankcase oils come with an additive package that is precisely developed. Introducing another additive disturbs that package and can even be detrimental. The simple truth is that the best practice for crankcase oil is to change it and keep it clean. Also, diesel engines require oil that is rated for diesels and not just for gasoline engines. That rating is clearly indicated on the bottle, usually in several places. You should be familiar with both the viscosity and API rating that is required for your engine.