BMW B38 / B37 engine: faults and reliability

• B38 1.2 (B38A12, MINI One)

  since 2014 · 75–102 hp · B38A12

  With caution

  We have found no reliability data specific to this variant: we cannot say it is free of defects, only that we have found none documented. Check the maintenance history.^[5]

• B38 1.5 136 hp up to April 2015 (B38A15)

  2014–2015 · 136 hp · B38A15

  With caution

  Both long-term tests with engine failure at 100,000 km involved a 218i from this period; if you are buying a unit from before April 2015, verify that the bearing has already been replaced.^[1]

• B38 1.5 136-140 hp from April 2015 (B38A15 / B38B15)

  since 2015 · 136 hp · B38A15, B38B15

  Buy

  BMW says the bearing change eliminated the problem, and we have found no other serious, widespread fault documented in the press or by official bodies for these units.^[1]

• B38K15T0 231 hp (BMW i8)

  2014–2020 · 231 hp · B38K15T0

  With caution

  We have found no failure data for the i8's petrol engine; around 20,465 units were built and, as a niche hybrid, there is little public information, so check its history with an official service centre.^[7]

• B37 1.5 diesel 95-116 hp (B37C15K0 / B37C15U0), up to 2017

  2014–2017 · 95–116 hp · B37C15K0, B37C15U0

  Buy

  We have found no serious, widespread documented fault on the B37; the MINI Cooper D F56 in a 2026 feature clocked up a million kilometres on its original engine, although it is an isolated case.^[8]

• B37TÜ1 1.5 diesel 95-116 hp (from late 2017)

  since 2017 · 95–116 hp · B37C15K0, B37C15U0

  Buy

  Same mechanical basis as the earlier B37, with no serious documented faults; adds AdBlue, which means checking the level and condition of the system.^[9]

Buy: No known serious faults, or they have already been corrected, in this version. With caution: Worth buying if something specific is verified: history, a replaced part or a completed campaign. Avoid: High risk of a serious fault that is hard to check for or prevent.

1. 1Critical severityFrequency: RareLubricationB38 crankshaft thrust bearing failure (units before April 2015)The first units of the 136 hp 1.5 (up to April 2015) had a half-wedge crankshaft thrust bearing that failed in two long-term tests at about 100,000 km with heavy clutch use; BMW changed it to a 360-degree one.Appears at around 100,000 km

Severity colours: low, medium, high, critical. How we rate them

Manufacturer

BMW

Family

Familia modular B de BMW

Fuel

Petrol

Displacement

1,499 cm³

Cylinders

3

Fuel system

Turbo

Injection

Direct injection

Timing

Chain

Power

75–231 hp

Peak torque

320 Nm

Production

since 2014

Makes

BMW and MINI

Technical data^[4][5][6]

1. since 2014

   B38 1.2 (B38A12, MINI One)

   1.2-litre variant of the three-cylinder family, with 55 kW (75 hp) and 75 kW (102 hp) according to German Wikipedia; fitted to the third-generation MINI One.^[5][13]

2. 2014–2015

   B38 1.5 136 hp up to April 2015 (B38A15)

   First units of the 1.5 with 100 kW (136 hp), with the half-wedge crankshaft thrust bearing; BMW replaced it with a 360-degree one from April 2015, and earlier units could be retrofitted through a service action.^[1][5]

3. 2014–2020

   B38K15T0 231 hp (BMW i8)

   High-performance version of the 1.5: 170 kW (231 hp) and 320 Nm, working alongside an electric motor in the BMW i8 plug-in hybrid (coupé 2014-2020, roadster 2018-2020).^[4][7]

4. 2014–2017

   B37 1.5 diesel 95-116 hp (B37C15K0 / B37C15U0), up to 2017

   1,496 cc three-cylinder diesel with a variable-geometry turbo and common rail: 70 kW (95 hp) and 220 Nm, or 85 kW (116 hp) and 270 Nm.^[6][10]

5. since 2015

   B38 1.5 136-140 hp from April 2015 (B38A15 / B38B15)

   The most widely used version (MINI Cooper, 118i, 218i, 318i, X1 sDrive18i, X2 sDrive18i). With the 360-degree bearing from April 2015; since March 2018 it has a petrol particulate filter (OPF), and the TÜ1 update announced by BMW in 2016 brought +5 kW, 350 bar injection and a separate cylinder head circuit.^[1][5][12]

6. since 2017

   B37TÜ1 1.5 diesel 95-116 hp (from late 2017)

   November 2017 update: selective catalytic reduction with AdBlue, particulate filter, 2,200 bar injection pressure and new cylinders and pistons to reduce noise, to meet Euro 6c.^[9][10]