BMW M54 vs Mitsubishi PHEV: which engine is more reliable?

According to our risk index, the Mitsubishi PHEV carries less risk than the BMW M54: 24/100 (low risk) versus 54/100 (high risk). The BMW M54 has 2 documented serious faults, the main one being «Thermostat and water pump failure»; the Mitsubishi PHEV has 2 documented serious faults, the main one being «Corroded air flow sensor: the petrol engine does not start to charge the battery».

Risk index

BMW M54

High risk · 2 serious faults

Risk index

Mitsubishi PHEV

Low 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 8 October 202614 sources How we work

Is the BMW M54 reliable?

The BMW M54 (2000-2006) is a naturally aspirated petrol inline-six with a reputation for longevity, passing 200,000 km if maintained. Its weak points are the crankcase ventilation valve and the plastic cooling system; check that they have been renewed.^[1][2][3]

See the 5 of the BMW M54 faults

Is the Mitsubishi PHEV reliable?

Yes, with caveats: the OCU ranks the Outlander PHEV first for reliability among used plug-in hybrids. What is documented are isolated campaigns (spark plugs and software, air flow sensor, fuel hose) and a possible loss of battery capacity, cited by one source and one study without figures. The Eclipse Cross PHEV, which uses the same system, has no documented faults of its own.^{[4][5][6][7][8]}

See the 5 of the Mitsubishi PHEV faults

Side-by-side comparison

Comparison of BMW M54 and Mitsubishi PHEV
Item	BMW M54	Mitsubishi PHEV
Technical data
Type	Engine	Engine
Fuel	Petrol	Petrol
Displacement	—	—
Timing	Chain	Chain
Power	170–235 hp	163–224 hp
Production	2000–2006^[9][10]	since 2013^[11][12][13]
Reliability
Risk index (what is it?)	54High risk	24Low risk
Documented faults	5	5
Of high or critical severity	2	2
Worst severity	High severity	High severity
Main faults	High severity: Thermostat and water pump failure High severity: Cracked expansion tank and coolant leak Medium severity: Cracked crankcase ventilation valve (CCV) and oil consumption	Medium severity: Loss of traction battery (high-voltage) capacity Medium severity: Spark plugs and petrol engine software on the Outlander PHEV (campaign R3033111) High severity: Corroded air flow sensor: the petrol engine does not start to charge the battery
Most expensive documented repair	No reliable data	No reliable data
Which versions to buy
BuyRecommended versions	None	2.4 Eclipse Cross PHEV (4B12, 13.8 kWh battery, 2021-2024)^[7][8]
With cautionVersions to be cautious about	M54B22, 2.2 litres (168-170 hp)^[1][2][3] M54B25, 2.5 litres (189-192 hp)^[1][2][3] M54B30, 3.0 litres (228-235 hp)^[1][2][3]	2.0 Outlander PHEV (4B11, 12 kWh battery, 2013-2018)^[6][7][14] 2.4 Outlander PHEV (4B12, 13.8 kWh battery, 2018-2021)^[4][5][6]
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 M54

Mitsubishi PHEV

Other comparisons

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With the Mitsubishi PHEV

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Sources

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

BMW M54 Engine Guide: Reliability, Common Problems & Tuning PotentialEuro Premium Parts · Technical documentation · consulted 5 October 2026
Il motore da 6 cilindri che supera agilmente i 300.000 kmAutoblog.it · Motoring press · published 13 February 2026 · consulted 5 October 2026 · in Italian
BMW M54 reliabilityAutoscore · Other source · consulted 5 October 2026
Mitsubishi Outlander PHEV, el híbrido enchufable de segunda mano más fiable según la OCUHíbridos y Eléctricos · Motoring press · published 14 May 2024 · consulted 8 October 2026 · in Spanish
Mitsubishi Outlander (II & III) – Bekannte Probleme und MängelGebrauchtwagenberater (Alemania) · Motoring press · published 2 March 2023 · consulted 8 October 2026 · in German
Baterías de híbrido enchufable: cuándo habrá que sustituirlas (Outlander PHEV)Autofácil · Motoring press · published 7 May 2020 · consulted 8 October 2026 · in Spanish
DVSA – base de llamadas a revisiónDVSA (Reino Unido) · Other source · consulted 8 October 2026
El Mitsubishi Eclipse Cross PHEV sí llegará a Europa, incluida España, en 2021Híbridos y Eléctricos · Motoring press · published 18 October 2020 · consulted 8 October 2026 · in Spanish
BMW M54Wikipedia (inglés) · Other source · consulted 5 October 2026
BMW M54Wikipedia (alemán) · Other source · consulted 5 October 2026 · in German
Mitsubishi Outlander PHEVWikipedia (inglés) · Other source · consulted 8 October 2026
Mitsubishi OutlanderWikipedia (alemán) · Other source · consulted 8 October 2026 · in German
Mitsubishi 4B1 engineWikipedia (inglés) · Other source · consulted 8 October 2026
Mitsubishi Outlander PHEV (2013 – 2014): alerta A12/1947/19 (sensor de caudal de aire)car-recalls.eu (alertas Safety Gate / RAPEX) · Other source · published 13 December 2019 · consulted 8 October 2026