I think some of psfred's info is incorrect. He says the W116 first had the non-turbo engine and began production in 1975. I believe the W116 diesels were all turbos (at least in the American market), and their official first year of production was in 1977, when 51 units were produced. He says W116 diesel production ran from 1975-1981; actually, the run was from 1977-1980.
He says that W126 5-cylinder diesel production began in 1982; actually it began in 1979, with 3 units produced.

I got this information from W. Robert Nitske's book, Mercedes-Benz Diesel Automobiles. Just thought I'd clarify things.

Joe Bauers
bauersjo@soltec.net