1983 300SD Turbo Diesel

[Cisco]

My car just turned to 140K miles. I have the car for almost three months and I've driven about 3,500 miles. The more I drive the car, the more I fall in love with it. However, I've noticed that it smokes a bit too much. I've observed other same model cars in the street, and they do not smoke as much as mine. The car doesn't burn oil. I check the oil on a regular basis, and never have to add any oil. I was told that a tuneup consist of just replacing the oil and the filters for the oil, air, and fuel. I replaced only one fuel filter(it looks like a regular oil filter). Are there other filters that should replace as well?
I was also told that it's a good practice to put one galon of kerozene for every full tank of diesel.
Any advised will be appreciated.

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