e-Skyactiv D 3.3 vs OM656: which engine is more reliable?

According to our risk index, the e-Skyactiv D 3.3 carries less risk than the OM656: 21/100 (low risk) versus 39/100 (moderate risk). The e-Skyactiv D 3.3 has 2 documented serious faults, the main one being «Stalling and restart failures due to control unit software»; the OM656 has 2 documented serious faults, the main one being «Leak in the vacuum-driven coolant pump (fire risk)».

Risk index

e-Skyactiv D 3.3

Low risk · 2 serious faults

Lower risk

Risk index

OM656

Moderate risk · 2 serious faults

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

Reviewed on 30 October 202613 sources How we work

Is the e-Skyactiv D 3.3 reliable?

The e-Skyactiv D 3.3 is an inline-six diesel with mild-hybrid assistance that Mazda debuted in the CX-60. It is a very recent engine: there is no in-service reliability data, and what is documented are software recalls (stalling, restarting, clutch) fixed at the official dealer.^[1][2][3]

See the 2 of the e-Skyactiv D 3.3 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.^{[1][4][5][6][7][8][9][10]}

See the 4 of the OM656 faults

Side-by-side comparison

Comparison of e-Skyactiv D 3.3 and OM656
Item	e-Skyactiv D 3.3	OM656
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	3,283 cm³	2,925 cm³
Timing	—	Chain
Power	254 hp	272–367 hp
Production	since 2022^[11][12]	since 2017^[4][5][13]
Reliability
Risk index (what is it?)	21Low risk	39Moderate risk
Documented faults	2	4
Of high or critical severity	2	2
Worst severity	High severity	Critical severity
Main faults	High severity: Stalling and restart failures due to control unit software High severity: Clutch between engine and electric motor that does not re-engage after braking	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)^[1][7][9]
With cautionVersions to be cautious about	3.3 e-Skyactiv D 254 (T3-VPTS, 2022-present)^[1][2][3]	OM656 2.9 diesel 350 d (OM 656 D 29 R SCR, from 2017)^[1][6][7] OM656 2.9 diesel 400 d (OM 656 D 29 SCR, from 2017)^[1][6][7][9]
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

e-Skyactiv D 3.3

Mazda CX-60

OM656

See the 11 models with the OM656

Other comparisons

With the e-Skyactiv D 3.3

With the OM656

Compare other engines

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Sources

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

DVSA – base de llamadas a revisión (Mazda CX-60)DVSA (Reino Unido) · Official body · consulted 29 October 2026
Mazda CX-60 (2022 – 2024): engine stall (Safety Gate SR/01913/25)Car-Recalls.eu · Official body · published 23 May 2025 · consulted 29 October 2026
Mazda CX-60: The engine not responding to the accelerator after stopping (KBA 14131R)Car-Recalls.eu · Official body · published 11 August 2025 · consulted 29 October 2026
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
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
Skyactiv (apartado Skyactiv-D 3.3)Wikipedia (inglés) · Other source · consulted 29 October 2026
Mazda CX-60 3.3 e-Skyactiv D MHEV 254ps AWD HomuraPractical Caravan · Motoring press · consulted 29 October 2026
Mercedes-Benz S-Class (W222)Wikipedia · Other source · consulted 9 October 2026