BMW B38 / B37 vs 1.2 12V: which engine is more reliable?

According to our risk index, the BMW B38 / B37 carries less risk than the 1.2 12V: 20/100 (low risk) versus 57/100 (high risk). The BMW B38 / B37 has 1 documented serious fault, the main one being «B38 crankshaft thrust bearing failure (units before April 2015)»; the 1.2 12V has 2 documented serious faults, the main one being «Timing chain stretch and tensioner wear».

Risk index

BMW B38 / B37

Low risk · 1 serious fault

Lower risk

Risk index

1.2 12V

High 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 202618 sources How we work

Is the BMW B38 / B37 reliable?

BMW and MINI's three-cylinder B38 (petrol) and B37 (diesel) have no serious, widespread documented fault. The only problem reported in the press is the crankshaft thrust bearing on early B38 units (up to April 2015), corrected by BMW. BMW's EGR campaigns affect four- and six-cylinder diesels, not the B37.^[1][2][3]

See the 3 of the BMW B38 / B37 faults

Is the 1.2 12V reliable?

The 1.2 12V is a simple, low-power, naturally aspirated three-cylinder engine (54-70 hp), with two documented design faults: the timing chain tensioner, which can end up destroying the engine, and -on the Volkswagen Polo IV- a catalytic converter too close to the cylinder head that can burn the exhaust valves. Ignition coil failures are also common, and there are isolated cases of oil consumption and vibration.^{[4][5][6][7][8]}

See the 5 of the 1.2 12V faults

Side-by-side comparison

Comparison of BMW B38 / B37 and 1.2 12V
Item	BMW B38 / B37	1.2 12V
Technical data
Type	Engine	Engine
Fuel	Petrol	Petrol
Displacement	1,499 cm³	1,198 cm³
Timing	Chain	Chain
Power	75–231 hp	54–70 hp
Production	since 2014^[9][10][11]	2001–2014^[4][12][13]
Reliability
Risk index (what is it?)	20Low risk	57High risk
Documented faults	3	5
Of high or critical severity	1	2
Worst severity	Critical severity	Critical severity
Main faults	Critical severity: B38 crankshaft thrust bearing failure (units before April 2015) Medium severity: Coolant leaks and water pump or thermostat failure on the B38 Low severity: Carbon build-up on the B38's intake valves and injectors	Critical severity: Timing chain stretch and tensioner wear High severity: Cylinder head and valve damage from exhaust gas backflow (Volkswagen Polo IV) Medium severity: Higher-than-normal oil consumption
Most expensive documented repair	No reliable data	No reliable data
Which versions to buy
BuyRecommended versions	B38 1.5 136-140 hp from April 2015 (B38A15 / B38B15)^[1] B37 1.5 diesel 95-116 hp (B37C15K0 / B37C15U0), up to 2017^[14] B37TÜ1 1.5 diesel 95-116 hp (from late 2017)^[15]	None
With cautionVersions to be cautious about	B38 1.2 (B38A12, MINI One)^[10] B38 1.5 136 hp up to April 2015 (B38A15)^[1] B38K15T0 231 hp (BMW i8)^[16]	1.2 54/60 hp (AWY, BMD, BBM, 2001-2014)^[4][6] 1.2 64/70 hp (BME, CGPA, 2002-2014)^{[4][6][17][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

BMW B38 / B37

See the 14 models with the BMW B38 / B37

1.2 12V

See the 7 models with the 1.2 12V

Other comparisons

With the BMW B38 / B37

With the 1.2 12V

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Sources

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

BMW Dreizylinder: Dauertest-Probleme des B38 behoben?BimmerToday · Motoring press · published 5 October 2017 · consulted 4 October 2026 · in German
2024: BMW recall due to EGR coolers extended againcar-recalls.eu · Motoring press · published 28 March 2024 · consulted 4 October 2026
BMW diésel Europa: llamada a revisión por el EGR y riesgo de incendioDiariomotor · Motoring press · consulted 4 October 2026 · in Spanish
VW Polo 4 (9N): Typische Probleme & SchwachstellenGebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
Fiabilité et pannes de la Volkswagen Polo 4Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité et pannes de la Seat Ibiza (2008-2017)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Seat Ibiza III (2002-2008): Bekannte Probleme & KrankheitenGebrauchtwagenberater.de · Motoring press · consulted 27 September 2026 · in German
Fiabilité et pannes de la Seat Ibiza (2002-2008)Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
BMW B38 (Wikipedia)Wikipedia · Other source · consulted 4 October 2026
BMW B38 (Wikipedia, alemán)Wikipedia · Other source · consulted 4 October 2026 · in German
BMW B37 (Wikipedia)Wikipedia · Other source · consulted 4 October 2026
VW EA111Wikipedia (alemán) · Other source · consulted 27 September 2026 · in German
VW Polo IVWikipedia (alemán) · Other source · consulted 27 September 2026 · in German
Project one M: MINI Cooper D F56 fährt eine Million Kilometer in 12 JahrenBimmerToday · Motoring press · published 24 June 2026 · consulted 4 October 2026 · in German
BMW Baukasten-Diesel: Mehr Infos zur TÜ1 für B47 und B37BimmerToday · Motoring press · published 20 November 2017 · consulted 4 October 2026 · in German
BMW i8 (Wikipedia)Wikipedia · Other source · consulted 4 October 2026
Fiabilité et pannes de la Volkswagen Polo 5Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French
Fiabilité et pannes de la Skoda Fabia 2Fiches-auto.fr · Motoring press · consulted 27 September 2026 · in French