The 3.0L all-aluminum M189 with Bosch mechanical fuel injection is revered as a direct relative of the 300SL Gullwing motor and praised as a joy at speed, but it is repeatedly called hard to work on and difficult to find parts and experienced mechanics for. It is prized as a rare aluminum-block six, distinct from the later V8s that replaced it.
The M189 alloy inline-six and its Gullwing lineage
Mercedes-Benz 300SE (W112) Fintail · mechanical