The naturally aspirated 5.4L M113 V8 is the car's defining strength and is universally described as bulletproof, with owners and sellers citing 250k-500k mile capability given regular maintenance. Commenters frame it as one of the best V8s ever built and note plugs and coils as the main scheduled wear items around 100k-200k miles.
M113 5.4L V8 longevity and bulletproof reputation
Mercedes-Benz CLK55 AMG (C208) · mechanical