M50 and M52 vs 2.3 EcoBoost: which engine is more reliable?

According to our risk index, the 2.3 EcoBoost carries less risk than the M50 and M52: 41/100 (moderate risk) versus 52/100 (high risk). The M50 and M52 has 2 documented serious faults, the main one being «Cooling system failure (expansion tank, thermostat, pump and radiator)»; the 2.3 EcoBoost has 2 documented serious faults, the main one being «Focus RS cylinder head gasket and block: coolant entering the cylinders».

Risk index

M50 and M52

High risk · 2 serious faults

Risk index

2.3 EcoBoost

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 2 November 202618 sources How we work

Is the M50 and M52 reliable?

The M52 and its predecessor the M50 are six-cylinder petrol engines that the sources describe as durable: Enginescope considers 300,000 km routine with the cooling circuit looked after. Watch the plastic cooling parts, VANOS, crankcase ventilation and oil leaks and, in the aluminium-block M52s built from 1995 to March 1998, cylinder wear caused by sulphur (Nikasil).^[1][2][3]

See the 5 of the M50 and M52 faults

Is the 2.3 EcoBoost reliable?

The 2.3 EcoBoost is the turbocharged four-cylinder petrol engine that Ford has fitted since 2015 to the Focus RS (350 hp), the fourth-generation Focus ST (280 hp) and the Ranger. Its documented fault is the cylinder head gasket on Focus RS cars built up to July 2017, which Ford repaired free of charge. We have found no evidence that it affects the ST, which uses a variant derived from the Mustang.^[4][5][6][7]

See the 3 of the 2.3 EcoBoost faults

Side-by-side comparison

Comparison of M50 and M52 and 2.3 EcoBoost
Item	M50 and M52	2.3 EcoBoost
Technical data
Type	Engine	Engine
Fuel	Petrol	Petrol
Displacement	—	2,261 cm³
Timing	Chain	Chain
Power	150–193 hp	270–350 hp
Production	1990–2001^{[8][9][10][11]}	since 2015^{[4][7][12][13]}
Reliability
Risk index (what is it?)	52High risk	41Moderate risk
Documented faults	5	3
Of high or critical severity	2	2
Worst severity	Critical severity	Critical severity
Main faults	High severity: Cooling system failure (expansion tank, thermostat, pump and radiator) Critical severity: Premature cylinder wear (Nikasil coating) Medium severity: Worn VANOS seals	Critical severity: Focus RS cylinder head gasket and block: coolant entering the cylinders High severity: Engine wiring harness damaged by the gearbox housing (fourth-generation Focus) Medium severity: Oil leaks from the filler cap, the oil cooler and the sump
Most expensive documented repair	No reliable data	No reliable data
Which versions to buy
BuyRecommended versions	None	2.3 EcoBoost 280 hp (Focus ST, 2019-2025)^[7][14]
With cautionVersions to be cautious about	M50B20, 2.0 litre (150 hp; 1990-1995)^[15][16] M50B25, 2.5 litre (192 hp; 1990-1995)^[15][16] M52B20, 2.0 litre (150 hp; 1994-1999)^[9][15] M52B25, 2.5 litre (170 hp; 1995-1999)^[9][15] M52B28, 2.8 litre (193 hp; 1995-1999)^[9][15][17] M52TUB20, 2.0 litre (150 hp; 1998-2001)^[8][15] M52TUB25, 2.5 litre (170 hp; 1998-2000)^[8][15] M52TUB28, 2.8 litre (193 hp; 1998-2001)^[3][8][15]	2.3 EcoBoost 350 hp (Focus RS, 2016-2018)^[5][6] 2.3 EcoBoost 270 hp (Ranger T6.2, Mexico, from 2023)^[13] 2.3 EcoBoost PHEV 281 hp (Ranger plug-in hybrid, from 2025)^[13][18]
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

M50 and M52

2.3 EcoBoost

Other comparisons

With the M50 and M52

With the 2.3 EcoBoost

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Sources

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

BMW 3 Series E36 320i (M52B20): reliabilityEnginescope · Other source · consulted 2 November 2026
BMW M52 reliabilityAutoscore · Other source · consulted 2 November 2026
BMW M52 Engine: Performance, Reliability, and TuningBMWBlog · Motoring press · consulted 2 November 2026
Ford EcoBoost engineWikipedia · Other source · consulted 2 November 2026
Ford Focus RS (Mk3) | PH Used Buying GuidePistonHeads · Motoring press · consulted 2 November 2026
Ford Focus RS engine problems: owners promised free repairsevo · Motoring press · published 23 January 2018 · consulted 2 November 2026
Ford Focus ST (Mk4) | PH Used Buying GuidePistonHeads · Motoring press · published 19 November 2023 · consulted 2 November 2026
BMW M52Wikipedia (inglés) · Other source · consulted 2 November 2026
BMW M52Wikipedia (alemán) · Other source · consulted 2 November 2026 · in German
BMW M50Wikipedia (inglés) · Other source · consulted 2 November 2026
BMW M50Wikipedia (alemán) · Other source · consulted 2 November 2026 · in German
Ford Focus RS (tabla del Focus RS Mk3, 2015-2018)Wikipedia · Other source · consulted 2 November 2026 · in German
Ford Ranger (T6)Wikipedia · Other source · consulted 2 November 2026
Used Ford Focus ST (Mk4, 2019 to date) review and buyer's guideevo · Motoring press · published 4 August 2022 · consulted 2 November 2026
BMW M50 / M52: problemas conocidosEnginescope · Other source · consulted 2 November 2026
Der BMW M50 Motor: Technische Daten, Probleme, Haltbarkeit & FahrzeuglisteCarWiki.de · Other source · consulted 2 November 2026 · in German
BMW Z3 Reliability Guide: Everything You Need to Know Before BuyingEuro Premium Parts · Technical documentation · consulted 2 November 2026
Ford Ranger (tabla del Ranger Plug-in-Hybrid)Wikipedia · Other source · consulted 2 November 2026 · in German