Skyactiv-D vs OM656: which engine is more reliable?

According to our risk index, the OM656 carries less risk than the Skyactiv-D: 39/100 (moderate risk) versus 55/100 (high risk). The Skyactiv-D has 3 documented serious faults, the main one being «Oil dilution with diesel during DPF regenerations»; the OM656 has 2 documented serious faults, the main one being «Leak in the vacuum-driven coolant pump (fire risk)».

Risk index

Skyactiv-D

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 202621 sources How we work

Is the Skyactiv-D reliable?

The Skyactiv-D is a modern and generally reliable diesel, but across its three displacements (1.5, 1.8 and 2.2) it shares oil dilution with diesel fuel during diesel particulate filter regenerations, which means you need to watch the oil level and not stretch oil changes, especially on short journeys; the older 2.2s (2012-2014) also accumulate more turbo and carbon build-up cases.^[1][2][3][4]

See the 4 of the Skyactiv-D 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 Skyactiv-D and OM656
Item	Skyactiv-D	OM656
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	—	2,925 cm³
Timing	Chain	Chain
Power	105–184 hp	272–367 hp
Production	since 2012^[1][13][14]	since 2017^[5][6][15]
Reliability
Risk index (what is it?)	55High risk	39Moderate risk
Documented faults	4	4
Of high or critical severity	3	2
Worst severity	Critical severity	Critical severity
Main faults	High severity: Oil dilution with diesel during DPF regenerations High severity: Turbo wear or failure from lack of lubrication Critical severity: Oil pump chain breakage and camshaft wear	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	No reliable data	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	2.2 Skyactiv-D 150/175 (SH-VPTS, 2012-2017)^[2][16][17] 2.2 Skyactiv-D 150/175/184 (SH-VPTS, 2017-2021)^[3][18] 1.5 Skyactiv-D 105 (S5-DPTS, 2015-2018)^[4][19] 1.8 Skyactiv-D 116 (S8-DPTS, 2018-present)^[4][20][21]	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

Skyactiv-D

See the 7 models with the Skyactiv-D

OM656

See the 11 models with the OM656

Other comparisons

With the Skyactiv-D

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.

SkyActivWikipedia (inglés) · Other source · consulted 27 September 2026
Fiabilité Mazda CX-5 (2012-2017)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda 6 (2012-2022)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda CX-3Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
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
Mazda CX-5Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Mazda3Wikipedia (inglés) · Other source · consulted 27 September 2026
Mercedes-Benz S-Class (W222)Wikipedia · Other source · consulted 9 October 2026
Aviso a todos los propietarios de Mazda CX-5 Dieselkm77 · Motoring press · published 22 May 2013 · consulted 27 September 2026 · in Spanish
Mazda6Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Fiabilité Mazda CX-5 II (2017-)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda 3 (2013-2019)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda CX-30Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda 3 (2019-)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French