1.6 CRDi vs OM656: which engine is more reliable?

According to our risk index, the OM656 carries less risk than the 1.6 CRDi: 39/100 (moderate risk) versus 70/100 (high risk). The 1.6 CRDi has 4 documented serious faults, the main one being «MHSG belt tensioner and crankshaft pulley failure (48V mild hybrid)»; the OM656 has 2 documented serious faults, the main one being «Leak in the vacuum-driven coolant pump (fire risk)».

Risk index

1.6 CRDi

High risk · 4 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 202620 sources How we work

Is the 1.6 CRDi reliable?

The U2 D4FB (2009-2018) is a generally robust diesel if well maintained, with known turbo failures in the early units and timing chain problems from 120,000-150,000 km. Its successor, the Smartstream (U3 D4FE, from 2018), has a good reputation, except in the 48V mild hybrid version, which has a belt tensioner and crankshaft pulley fault that can destroy the engine.^[1][2][3]

See the 6 of the 1.6 CRDi 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.^{[4][5][6][7][8][9][10][11]}

See the 4 of the OM656 faults

Side-by-side comparison

Comparison of 1.6 CRDi and OM656
Item	1.6 CRDi	OM656
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	1,582 cm³	2,925 cm³
Timing	Chain	Chain
Power	90–136 hp	272–367 hp
Production	since 2009^{[1][12][13][14]}	since 2017^[4][5][15]
Reliability
Risk index (what is it?)	70High risk	39Moderate risk
Documented faults	6	4
Of high or critical severity	4	2
Worst severity	Critical severity	Critical severity
Main faults	Critical severity: MHSG belt tensioner and crankshaft pulley failure (48V mild hybrid) Critical severity: Timing chain stretch High severity: Premature variable-geometry turbo (VGT) failure	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 €1,800Particulate filter (DPF) blocked in urban usePublished figure^[16]	No reliable data
Which versions to buy
BuyRecommended versions	Smartstream 1.6 CRDi U3 (D4FE, 115-136 hp, without mild hybrid, from 2018)^[2][17]	OM656 3.0 diesel with electric assistance (D 30, from 2023)^[7][8][10]
With cautionVersions to be cautious about	1.6 CRDi U2 (D4FB, 90-136 hp, sold in Spain from 2010 to ~2018)^[1][18][19] Smartstream 1.6 CRDi 48V mild hybrid (D4FE MHEV, 136 hp, from ~2019)^[3][20]	OM656 2.9 diesel 350 d (OM 656 D 29 R SCR, from 2017)^[6][7][8] OM656 2.9 diesel 400 d (OM 656 D 29 SCR, from 2017)^{[6][7][8][10]}
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

1.6 CRDi

See the 16 models with the 1.6 CRDi

OM656

See the 11 models with the OM656

Other comparisons

With the 1.6 CRDi

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.

Motor Kia y Hyundai 1.6 CRDI (D4FB): ficha tecnica, problemas y tuningMotordinámico · Technical documentation · consulted 26 September 2026 · in Spanish
Kia Ceed III: Bekannte Probleme & RückrufeGebrauchtwagenberater · Other source · consulted 26 September 2026 · in German
Kia / Hyundai 1.6 CRDi MHEV Engine FailuresDOHC (especialista en reconstrucción de motores) · Technical documentation · consulted 26 September 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
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
Hyundai U engineWikipedia · Other source · consulted 26 September 2026
Hyundai Smartstream engineWikipedia · Other source · consulted 26 September 2026
Hyundai i30 Kombi 1.6 CRDi 48V-Mildhybrid Trend (10/20-01/22): Technische Daten, Bilder, PreiseADAC · Technical documentation · consulted 26 September 2026 · in German
Mercedes-Benz S-Class (W222)Wikipedia · Other source · consulted 9 October 2026
Kia Ceed 1.6 Crdi Problemas | Fallos y averías más frecuentesTotalRenting · Other source · consulted 26 September 2026 · in Spanish
Kia Ceed im TÜV-Check 2026: Schwachstellen, Mängel und ProblemeAUTO BILD · Motoring press · published 2026 · consulted 26 September 2026 · in German
Kia and Hyundai 1.6 CRDI (D4FB) engineEngineDNA · Other source · consulted 26 September 2026
Best Hyundai Kia 1.6 CRDI Mods & Upgrades Guide to D4FB TuningTorqueCars · Other source · consulted 26 September 2026
KIA SPORTAGE 2023 - vehicle recallsGOV.UK (Driver and Vehicle Standards Agency) · Official body · consulted 26 September 2026