BMW B57 vs MZR-CD: which engine is more reliable?

According to our risk index, the BMW B57 carries less risk than the MZR-CD: 22/100 (low risk) versus 64/100 (high risk). The BMW B57 has 3 documented serious faults, the main one being «EGR cooler leaks on the B57 (limited action on the 540d xDrive)»; the MZR-CD has 3 documented serious faults, the main one being «Timing chain stretch on the 2.2 MZR-CD».

Risk index

BMW B57

Low risk · 3 serious faults

Lower risk

Risk index

MZR-CD

High risk · 3 serious faults

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

Reviewed on 4 October 202617 sources How we work

Is the BMW B57 reliable?

The BMW B57 (2015 onwards) is the six-cylinder diesel that succeeded the N57. The sources consulted document no widespread faults: its most cited weak point is the AdBlue/SCR system, and it was left out of the big EGR campaigns that hit the N47 and N57. The timing chain is still at the back, next to the gearbox.^[1][2]

See the 4 of the BMW B57 faults

Is the MZR-CD reliable?

The MZR-CD is Mazda's most widespread diesel between 2002 and 2013, fitted to the Mazda3, Mazda6, Mazda5 and CX-7. It is sensitive to short journeys: the injector seals and incomplete DPF regenerations can dilute the oil, and the EGR and intake build up carbon. The 2.2-litre redesign (from 2008), with a timing chain instead of a belt, adds the risk of that chain stretching and damaging the engine.^[3][4][5][6]

See the 4 of the MZR-CD faults

Side-by-side comparison

Comparison of BMW B57 and MZR-CD
Item	BMW B57	MZR-CD
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	2,993 cm³	—
Timing	Chain	Timing belt (dry)
Power	265–400 hp	105–185 hp
Production	since 2015^[7][8]	2002–2013^{[9][10][11][12][13]}
Reliability
Risk index (what is it?)	22Low risk	64High risk
Documented faults	4	4
Of high or critical severity	3	3
Worst severity	High severity	Critical severity
Main faults	Medium severity: AdBlue/SCR system fault (NOx sensors, heater and pump) High severity: EGR cooler leaks on the B57 (limited action on the 540d xDrive) High severity: Timing chain wear on the gearbox side	Critical severity: Timing chain stretch on the 2.2 MZR-CD High severity: Oil dilution from leaking injector seals and DPF regenerations High severity: Turbocharger wear or failure
Most expensive documented repair	No reliable data	No reliable data
Which versions to buy
BuyRecommended versions	B57D30 265 hp, single turbo (B57D30O0, 2015-2020)^[1] B57D30 286-340 hp, twin turbo with 48 V (B57D30O2/T2, 2020 onwards)^[1]	None
With cautionVersions to be cautious about	B57D30 320 hp, twin turbo (B57D30T0, 2015-2020)^[1] B57D30 400 hp, four turbos (B57D30S0, 2016-2020)^[1]	2.0 MZR-CD 121-143 (RF, 2002-2005, no DPF)^[3][5][14] 2.0 MZR-CD 105-143 (RF, 2005-2010, with DPF)^{[3][5][14][15]} 2.2 MZR-CD 125-185 (R2, 2008-2013)^{[4][6][16][17]}
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 B57

See the 9 models with the BMW B57

MZR-CD

Other comparisons

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With the MZR-CD

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Sources

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

Motor BMW B57: fiabilidad y averíasDasercars · Motoring press · consulted 4 October 2026 · in Spanish
Motor BMW N57: diferencias con el B57Dasercars · Motoring press · consulted 4 October 2026 · in Spanish
Fiabilité Mazda 6 (2002-2008)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité Mazda 6 (2008-2013)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Mazda 6 I: Bekannte Probleme und Schwachstellengebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
Mazda 6 II: Bekannte Probleme und Schwachstellengebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
BMW B57 (Wikipedia en)Wikipedia · Other source · consulted 4 October 2026
BMW B57 (Wikipedia de)Wikipedia · Other source · consulted 4 October 2026 · in German
Mazda diesel enginesWikipedia (inglés) · Other source · consulted 27 September 2026
Mazda6Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Mazda3Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Mazda5Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Mazda CX-7Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Fiabilité Mazda 3 (2003-2009)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Japanische Zuverlässigkeit? Ärger mit den Dieseln von Mazda und Toyotagebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
Fiabilité Mazda 3 (2009-2013)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Mazda 3 II (2009-2013): Typische Probleme & Schwachstellengebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German