About ten years ago I noted a lack of power in my 1983 300SD. At the time I thought that a car with a little over 100,000 miles has a right to grow old and die. About a month later I was talking to another diesel owner (boat) and was told that the fuel has changed and I should try adding diesel Power Service cetane boost (gray bottle). First, I had to get a bottle that counts off an ounce at a time and add one ounce for every three gallons I used to fill up the tank. From there I could change the ratio as needed.
I added one ounce for each three gallons in my car diesel (back to normal) as well as to my boat diesel (no difference). I have not had any problems since and am still on the original injectors.
I was wondering if anybody on this forum has played with the ratio of this or other additives. Now I live in a warm climate so I would not have to adjust for cold starts, but I was thinking once you reach a normal cetane level there should be no advantage to adding more. What do you think?