Yes, I know the catalytic converter in the 87 diesel (mine has one). All gas cars have catalytic converter and additive does not hurt them. What I tried to say is that the trap did not like additives but the catalytic converter is OK with addtives.
Many diesel fuels (#1 or premium) contain the same additives we can buy.
I use Power Service additives (two different kinds). One is more for cleaning and the other for ant-gel, etc. Both have some cetane boosts.
I have only been using it since Nov when I bought the car. The previous owner started using it after the trap recall (replaced with the catalytic converter) and she told me the MB shop service person told her to use because of the poor and inconsistent diesel quality.
I tried a few times without the additive and I observe noticeable roughness.
I know Lance on this forum who also has a 87 300SDL with over 250kmi. He uses Power Serice and Amsoil cetane boots.