If no one else answers, my opinion is the W126 (ending M.Y.1991) diesels are good, so long as you stay away from the bored-out 350SDL engine. They do not have so much more electronics and the parts are only a little more expensive. However, as you know, you simply can not beat the price/reliablity/servicibility combo of the W123 you are already in. To recommend a specific car, I would look to the last year of the reliable engine: 1987 300SDL longbody turbodiesel. Cheers, Andrew Seidel.
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