Back in the 1980's while living in Bartlesville, OK, it was common to see W123 with 240 Turbodiesel logo on trunk lid. Looked factory so I researched it and found MB didn't market a turbo 240D. Those cars (probably 3 or 4) had been modified for fuel economy studies by the Bartlesville Department of Energy facility. Don't know what happened to those cars but certainly government documentation was produced from that study.