BMW B47 vs OM656: which engine is more reliable?

According to our risk index, the OM656 carries less risk than the BMW B47: 39/100 (moderate risk) versus 73/100 (high risk). The BMW B47 has 3 documented serious faults, the main one being «EGR cooler leaks with risk of engine fire»; the OM656 has 2 documented serious faults, the main one being «Leak in the vacuum-driven coolant pump (fire risk)».

Risk index

BMW B47

High risk · 3 serious faults

Risk index

OM656

Moderate risk · 2 serious faults

Lower risk

The index (0–100) weights the severity and frequency of the three most serious documented faults. How it is calculated

Reviewed on 9 October 202613 sources How we work

Is the BMW B47 reliable?

The BMW B47 (since 2014, successor to the N47) improves the timing chain tensioner, guides and oil supply and greatly reduces the failure rate of its predecessor, but it is not free of problems: the EGR cooler has been the subject of several BMW technical campaigns for engine fire risk since 2018, and the turbo and particulate filter need careful maintenance.^[1][2][3][4]

See the 4 of the BMW B47 faults

Is the OM656 reliable?

The OM656 is the roughly 3.0-litre in-line six-cylinder diesel with which Mercedes-Benz replaced the OM642 V6 from 2017 in the S-Class, E-Class, CLS, GLE, GLS and G-Class (350 d, 400 d and 450 d). It has few documented faults: the known campaign is the coolant pump one of 2021-2022, and the timing chain recall that circulates belongs to the OM654. Guides warn about the AdBlue/SCR system, the EGR and, in isolated cases, the roller rocker arms, without figures.^{[5][6][7][8][9][10][11][12]}

See the 4 of the OM656 faults

Side-by-side comparison

Comparison of BMW B47 and OM656
Item	BMW B47	OM656
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	1,995 cm³	2,925 cm³
Timing	Chain	Chain
Power	114–228 hp	272–367 hp
Production	since 2014^[1]	since 2017^[5][6][13]
Reliability
Risk index (what is it?)	73High risk	39Moderate risk
Documented faults	4	4
Of high or critical severity	3	2
Worst severity	Critical severity	Critical severity
Main faults	Critical severity: EGR cooler leaks with risk of engine fire High severity: Timing chain wear (improved, but is it really at the front?) High severity: Premature turbo wear from neglected maintenance	Critical severity: Leak in the vacuum-driven coolant pump (fire risk) Medium severity: NOx sensor failure and AdBlue (SCR) system warnings Medium severity: EGR valve clogged with soot after short journeys
Most expensive documented repair	up to €2,000Premature turbo wear from neglected maintenancePublished figure^[3]	No reliable data
Which versions to buy
BuyRecommended versions	None	OM656 3.0 diesel with electric assistance (D 30, from 2023)^[8][9][11]
With cautionVersions to be cautious about	B47 114-150 hp, single turbo (2014-)^[2][4] B47 168-190 hp, single turbo (2014-)^[2][4] B47 202-228 hp, twin-turbo (2015-)^[2][4] B47C20 (MINI Cooper D/SD and Countryman, 2014-)^[1][4]	OM656 2.9 diesel 350 d (OM 656 D 29 R SCR, from 2017)^[7][8][9] OM656 2.9 diesel 400 d (OM 656 D 29 SCR, from 2017)^{[7][8][9][11]}
AvoidVersions to avoid	None	None

Severity of each fault: green, low; amber, medium; red, high; dark red, critical. How we rate them

Cars that each one is fitted to

BMW B47

See the 19 models with the BMW B47

OM656

See the 11 models with the OM656

Other comparisons

With the BMW B47

With the OM656

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Sources

Every fact on this page links to its source. If you find an error, let us know.

BMW B47Wikipedia (inglés) · Other source · consulted 26 September 2026
324.000 diésel de BMW tendrán que pasar por el taller en Europa, por un posible riesgo de incendio en la EGRDiariomotor · Motoring press · published 8 August 2018 · consulted 26 September 2026 · in Spanish
Motor BMW B47: problemas, modelos y qué revisarCarexam · Motoring press · consulted 26 September 2026 · in Spanish
Motor BMW B47 - Reparación EspecializadaDasercars · Technical documentation · consulted 26 September 2026 · in Spanish
Mercedes-Benz OM656 engineWikipedia · Other source · consulted 9 October 2026
Mercedes-Benz OM 656Wikipedia (alemán) · Other source · consulted 9 October 2026 · in German
Rückruf für OM 656 und OM 654 Motoren wegen KühlmittelpumpeMBpassion · Motoring press · published 9 December 2021 · consulted 9 October 2026 · in German
Mercedes-Rückruf: Kühlmittelprobleme bei DieselautosAUTOHAUS · Motoring press · published 5 January 2022 · consulted 9 October 2026 · in German
DVSA – base de llamadas a revisiónDVSA (Reino Unido) · Other source · consulted 9 October 2026
Mercedes-Benz GLC (X253): Alle typischen Probleme & MängelGebrauchtwagenberater · Motoring press · consulted 9 October 2026 · in German
Mercedes OM656 Diesel: Häufige Probleme, Ursachen & Tipps zur Vermeidung von MotorschädenMBpassion · Motoring press · published 19 February 2026 · consulted 9 October 2026 · in German
Mercedes-Benz OM656 Engine Guide: Reliability, Common Problems & Tuning PotentialEuro Premium Parts · Technical documentation · consulted 9 October 2026
Mercedes-Benz S-Class (W222)Wikipedia · Other source · consulted 9 October 2026