The supercharged 5.4L M113K in the E55 is repeatedly described as essentially bulletproof, routinely reaching 150-200k+ miles on basic maintenance. Owners across many listings cite high-mileage cars still feeling strong, and frame the M113K's durability as a key reason to favor the E55.
M113K supercharged V8 'bulletproof' reputation (E55)
Mercedes-Benz E55/E63 AMG (W211) · mechanical