M278 vs OM656

Side-by-side reliability comparison

Higher reliability score
OM656 BUY 82/100
+20 points over M278
0 / 100
CAUTION M278 Mercedes-Benz
0 / 100
BUY OM656 Mercedes-Benz

Specifications

M278
OM656
Brand
Mercedes-Benz
Mercedes-Benz
Verdict
CAUTION
BUY
Reliability
62
82
Years
2010--2018
2017--present
Displacement
4663 cc
2999 cc
Layout
V8
I6
Type
Petrol Turbo
Diesel
Power
408--455 hp
243--330 hp
Known Issues
2
2
Total Risk Cost
€2,500--€9,500
€500--€2,000

Character

M278

"W222 S500, W166 GLE500, W212 E550. Hot-V twin-turbo. Timing chain guides. Turbo oil line leaks. Expensive timing chain job (engine-out in some models). Powerful but costly to own."

OM656

"Flagship modern MB diesel. Inline-6 smoothness returns. MHEV. GLE/GLS/S-Class. Excellent highway. Early data strong."

Issues Comparison

M278 2

◆ CRITICAL
Timing chain guide failure €2,000--€8,000 80,000 km--150,000 km
▲ HIGH
Turbo oil line leak €500--€1,500 60,000 km--120,000 km

OM656 2

● MODERATE
DPF + EGR — diesel city driving concern €400--€1,200 60,000 km--120,000 km
○ MINOR
AdBlue / SCR system consumption and faults €100--€800 30,000 km--∞

Models

M278 2

SL R231 2012--2018 S-Class W222 2013--2017

OM656 3

E 400d W213 2016--2024 Sedan GLE 350d W166 2015--2019 SUV S 350d W222 2013--2020 Sedan
Full M278 Report Full OM656 Report