Bulletin
Engine code

IA Technical Bulletin

BMW N20 and N26 Engine Guide

Engine: N20

Bulletin text

IAIK means IA-insiders knowledge, our collected BMW technical and ownership notes. Where a statement applies to only one engine, it says so; otherwise it applies to both.

N20B20O0 and N26B20O0 · 1,997 cc · turbocharged inline-4 · US builds 2011-2018 · 2 Series, 3 Series and 4 Series (N20 and N26) · 5 Series, X1, X3, X4, X5 xDrive40e and Z4 (N20 only)

The N20 is BMW's 2.0 liter turbocharged inline-four, displacing 1,997 cc. The N26 is the US-market SULEV version of the N20. BMW's training says the N20 brought the four-cylinder back to the US market after the M44 ended in 1999, phased in on a number of models from September 2011. BMW's training calls the N20 closely related to the N55, and both use TVDI, BMW's name for turbocharging combined with Valvetronic and direct injection. BMW's training says the N20 was to replace the N52 six-cylinder naturally aspirated engines. IAIK lists the US-market N26B20O0 as introduced in the F30 328i in March 2012. IAIK says the N26 shares most of the N20's mechanical core, and BMW's training puts the carry-over at over 95 percent. IAIK's summary view is that chain-drive condition and the N26 emissions-specific components deserve separate inspection.

Quick read

Ownership position: chain-drive condition and the N26 emissions-specific components deserve separate inspection.
Reliability: not established by IAIK as a rating. BMW's own documents point at the timing chain and oil pump drive chain, the coolant pump plug connector, and, on some early builds, the brake vacuum pump. From our own shop, IAIK adds oil filter housing, Valvetronic, injector, valve cover gasket and oil pan issues; see The Insider Read.
Cost to own: not established by IAIK; the dossier gives no cost figures.
Power potential: not established by IAIK. The factory rating in BMW's training is 240 hp and 350 Nm for both engines.
Main watch item: timing chain and oil pump drive chain. IAIK agrees from our shop: the timing chain is the item it expects on an N20.

Where you find it

This list shows the US-market cars the parts catalog carries with an N20 or an N26, with catalog build years. The N suffix (F10N, F30N, F31N) is the parts catalog's label for the later builds of that chassis.

Chassis	Engine	US models (catalog build years)
E84 X1	N20	X1 sDrive28i (2012-2015); X1 xDrive28i (2011-2015)
E89 Z4 roadster	N20	Z4 sDrive28i (2011-2016)
F10 5 Series sedan	N20	528i and 528i xDrive (2011-2013)
F10N 5 Series sedan	N20	528i and 528i xDrive (2013-2016)
F15 X5	N20	X5 xDrive40e (2015-2018)
F22 2 Series coupe	N20	228i (2013-2016); 228i xDrive (2014-2015)
F22 2 Series coupe	N26	228i and 228i xDrive (2014-2016)
F23 2 Series convertible	N20	228i and 228i xDrive (2014-2015)
F23 2 Series convertible	N26	228i and 228i xDrive (2015-2016)
F25 X3	N20	X3 sDrive28i (2014-2017); X3 xDrive28i (2012-2017)
F26 X4	N20	X4 xDrive28i (2014-2018)
F30 3 Series sedan	N20	320i (2012-2015); 320i xDrive (2013-2015); 328i (2011-2015); 328i xDrive (2012-2015)
F30 3 Series sedan	N26	328i and 328i xDrive (2012-2015)
F30N 3 Series sedan	N20	320i and 320i xDrive (2015-2018); 328i (2015-2016)
F30N 3 Series sedan	N26	328i and 328i xDrive (2015-2016)
F31 3 Series Sports Wagon	N20	328i xDrive (2013-2015)
F31N 3 Series Sports Wagon	N20	328i xDrive (2015-2016)
F32 4 Series coupe	N20	428i (2013-2016); 428i xDrive (2013-2015)
F32 4 Series coupe	N26	428i and 428i xDrive (2013-2016)
F33 4 Series convertible	N20	428i (2013-2015); 428i xDrive (2014-2015)
F33 4 Series convertible	N26	428i (2013-2016); 428i xDrive (2014-2016)
F34 3 Series Gran Turismo	N20	328i xDrive (2013-2015)
F34 3 Series Gran Turismo	N26	328i xDrive (2014-2016)
F36 4 Series Gran Coupe	N20	428i and 428i xDrive (2014-2015)
F36 4 Series Gran Coupe	N26	428i and 428i xDrive (2014-2016)

Both engines appear in the same US model lines, so a 228i, 328i or 428i can carry either an N20 or an N26. BMW's training places the engine designation and number on the crankcase behind the air conditioning compressor bracket. Check it there when the model name alone does not settle N20 versus N26. The catalog also lists the N20 in other model designations outside the US, which this guide does not cover.

N20 and N26 At a Glance

Question	Practical answer
Factory output	BMW's training lists 240 hp (180 kW) at 5,000-6,500 rpm and 350 Nm at 1,250-4,800 rpm for both engines.
Which engine is it?	The N20 is the ULEV II engine and the N26 is the SULEV engine. Both engines appear in the same US 2 Series, 3 Series and 4 Series models.
Reliability profile	IAIK names chain and guide condition as an important buying check on both engines and lists the N26 emissions-specific components as a separate check.
Best ownership indicator	IAIK points to records: chain work, cooling-system condition, oil leaks and any diagnosed ventilation or fuel-system faults. IAIK says a claim that the engine has been "bulletproofed" cannot replace those records.
Typical annual planning budget	Not established by IAIK; the dossier gives no cost figures.
Possible first-year catch-up	Not established by IAIK; the dossier gives no total.
Largest common repair exposure	IAIK does not rank repairs by cost. Its main inspection item is the chain drives. BMW's bulletins describe a chain repair that replaces the oil pump drive chain module, the timing chain, the tensioner, and the slide, tensioning and guide rails when diagnosis calls for it.
Tuned power levels	Not established by IAIK; the dossier gives no tuning ranges.
Before buying	Ask for the chain repair invoice and the parts used, and check cooling-system condition and oil leaks. Ask what was diagnosed on ventilation and fuel-system faults. Check the VIN for open recalls, including recall 24V-608 on the coolant pump plug connector.

Technical Specifications

Specification	Detail
Configuration	Both: longitudinal inline-four with one twin-scroll turbocharger.
Engine code	N20B20O0 (N20) and N26B20O0 (N26).
Displacement	1,997 cc, both engines.
Bore x stroke	84 mm bore x 90.091 mm stroke (N20); BMW's N26 training table lists both engines as 84/90.
Compression ratio	10.0:1, both engines.
Power and torque	240 hp (180 kW) at 5,000-6,500 rpm and 350 Nm at 1,250-4,800 rpm; cutoff speed 7,000 rpm. These figures describe the named training variants, not every vehicle carrying an N20 badge.
Firing order	1-3-4-2, both engines.
Valvetrain	Four valves per cylinder, Valvetronic III variable intake-valve lift and double VANOS; intake valves 32 mm and exhaust valves 28 mm; VANOS adjustment range 70 degrees on the intake side and 55 degrees on the exhaust side, in crankshaft angle.
Fuel system	Direct injection with Bosch HDEV5.2 solenoid injectors and system pressure up to 200 bar; single-plunger high-pressure pump driven from the exhaust camshaft.
Engine management	N20: Bosch MEVD17.2.4 in the initial training specification and MEVD17.2.9 from July 2012 production. N26: MEVD17.2.9.
Wastegate	N26 and every N20 built from July 2012: electric wastegate actuator. Earlier N20: vacuum-operated wastegate.
Emissions (US)	N20: ULEV II. N26: SULEV.
Engine oil	Model years 2012-2015: 0W-30 LL01FE. Model year 2016 and newer: 0W-20 LL14FE+. BMW's chart lists the N20 and N26 together.
Cooling	Electric coolant pump (400 W nominal) and a map thermostat, both managed by the engine electronics; the N26 cooling system is the same as the N20.
Oil pump	Map-controlled variable-delivery oil pump; oil pressure in map mode ranges from 1.5 to 4.5 bar, and the fail-safe mode limits it to 5.5 bar.
Crankshaft	Forged crankshaft on five lead-free bearings.
Block	Die-cast aluminium block with an electric-arc-sprayed iron cylinder coating.
Exhaust manifold and turbocharger	Air-gap-insulated four-into-two exhaust manifold welded to the turbocharger; cylinders 1 and 4 feed one scroll and cylinders 2 and 3 the other.

N20 and N26 compared

Item	N20	N26
US emissions standard	ULEV II	SULEV
Engine control unit	MEVD17.2.4, then MEVD17.2.9 from July 2012 production	MEVD17.2.9
Wastegate actuator	Vacuum-operated until July 2012 production, then electric	Electric
Catalytic converter monoliths	First monolith 600 cells per square inch, second 400	First monolith 900 cells per square inch, second 600
Wastegate vacuum reservoir	Built into the engine cover in BMW's N20 training	Not built into the engine cover
Crankcase pressure control valve	In the cylinder head cover	Welded to the cover and not replaced separately
Injectors	HDEV5.2 solenoid injectors	HDEV5.2, hand-selected after leak testing

Engine oil fill capacity

Chassis and drive (engine)	Fill capacity
E89 Z4 (N20)	5.3 quarts (5.0 liters)
F10 5 Series without all-wheel drive (N20)	5.3 quarts (5.0 liters)
F10 5 Series with all-wheel drive (N20)	5.0 quarts (4.75 liters)
F22 2 Series (N20)	5.3 quarts (5.0 liters)
F25 X3 and F26 X4 (N20)	5.1 quarts (4.8 liters)
F30, F31, F32, F33, F34, F36 without all-wheel drive (N20)	5.3 quarts (5.0 liters)
F30, F31, F32, F33, F34, F36 with all-wheel drive (N20)	5.1 quarts (4.8 liters)
F15 X5 xDrive40e plug-in hybrid (N20 with electric motor)	5.0 quarts (4.75 liters)
F22, F23, F30, F32, F33, F34, F36 without all-wheel drive (N26)	5.3 quarts (5.0 liters)
F22, F23, F30, F32, F33, F34, F36 with all-wheel drive (N26)	5.1 quarts (4.8 liters)

BMW's chart does not list the E84 X1 for these engines, so its capacity is not established here.

The Insider Read

IAIK describes the N26 as sharing most of the N20's mechanical core. It asks that an N20's mechanical repair history be kept apart from an N26's additional emissions-hardware requirements.

IAIK puts chain-drive condition first in its summary line. It describes an upper tooth-type chain that drives the camshafts and a separate lower drive that serves the oil pump and the counterbalance-shaft assembly.

IAIK says a useful pre-purchase record covers chain work, cooling-system condition, oil leaks and any diagnosed ventilation or fuel-system faults. It says a vague claim that the engine has been "bulletproofed" cannot replace those records.

IAIK also says assembly checks belong in the scope of the relevant repair, and that a shop should document nozzle engagement, DME mounting or pump-storage precautions when those parts are disturbed.

On the N26, IAIK says warranty eligibility for emissions hardware depends on the vehicle, the registration jurisdiction and the warranty terms, and that the N26 designation alone does not establish current coverage.

What IAIK sees in our shop

The notes in this part come from IAIK's own shop experience with the N20, not from BMW figures, and they are not failure rates.

In our shop the timing chain is the N20 item IAIK expects; beyond it, IAIK sees oil filter housing problems, Valvetronic issues, injector issues, valve cover gasket leaks and oil pan leaks.

IAIK also sees stripped oil pans and drain plugs from over-tightening, because some versions use a plastic drain plug and a plastic pan; see Known Failure Points for which cars BMW's repair data lists with them.

Factory Deep Dive

Both engines: TVDI with a twin-scroll turbocharger

IAIK describes the longitudinal N20 as combining a twin-scroll turbocharger, Valvetronic III variable intake-valve lift, double VANOS camshaft timing and direct injection. IAIK says TVDI describes how those systems work together: turbocharging supplies the air, valve lift helps meter it, and the injectors deliver fuel directly to the cylinders. BMW's training spells TVDI out as Turbocharged Valvetronic Direct Injection.

In the twin-scroll turbocharger, cylinders 1 and 4 feed one scroll and cylinders 2 and 3 feed the other, and BMW's training says this pulse charging gives a fast turbocharger response, especially at low engine speeds.

The turbocharger has an electric blow-off valve. On the N26 and on every N20 built from July 2012 the wastegate is driven by an electric actuator, and earlier N20 engines use a vacuum-operated wastegate. N26 only: BMW's training says the N26's electric wastegate actuator is there to help the catalytic converter heat up quickly enough to meet SULEV limits.

Both engines: block, cylinder coating and crankshaft

IAIK says the aluminium crankcase uses electric arc wire-sprayed cylinder running surfaces. BMW's training says the coating is about 1 mm thick and cannot be reworked in service, so a cylinder that is out of specification means replacing the whole engine block.

The crankshaft is forged and runs on five lead-free bearings, and the crank drive combines a positive crankshaft offset with a negative piston pin offset. BMW's training lists the crankshaft stroke as 89.6 mm and shows a stroke of 90.09 mm in its crankshaft-offset data; the specification table quotes 90.091 mm. N26 only: BMW's training says the N26 shares the cylinder head, valvetrain, engine block, crankshaft and pistons with the N20.

Both engines: two chain drives and the oil pump

IAIK says the upper tooth-type chain drives the camshafts and a separate lower drive serves the oil pump and counterbalance-shaft assembly. BMW's training says both chains are tooth-type, and that the lower chain turns the counterbalance shafts, which drive the oil pump through gears. IAIK says a timing-chain repair record should name the components actually inspected or replaced instead of saying "chain done".

BMW's training says the oil pump cannot be replaced on its own: the whole unit, including the counterbalance shafts, is replaced if the pump fails. BMW's training says the oil-to-coolant heat exchanger sits ahead of the oil filter, so the oil is cooled before it is filtered.

Both engines: crankcase ventilation and the cylinder head cover

BMW's training describes a two-mode crankcase ventilation system built into the cylinder head cover. In naturally aspirated mode the pressure control valve regulates crankcase vacuum at about 38 mbar; in boost mode the gases are drawn off through the fresh-air pipe ahead of the turbocharger and the pressure control valve is bypassed. BMW's recall filing for the coolant pump plug connector says blow-by liquid from this ventilation system may collect on the intake air hose and drip onto the plug connector.

N26 only: the crankcase pressure-regulating valve is welded into the cylinder head cover, and BMW's training says it is no longer replaced separately. N26 only: IAIK says a confirmed valve failure therefore changes the repair plan toward the cylinder-head-cover assembly, and that the fault and the cover actually fitted should be established first. The parts catalog lists two different cylinder head cover part numbers across these engines: 11 12 7 588 412 appears only on N20 cars, and 11 12 7 633 630 appears on N26 cars and on a few later F30N N20 cars. Match the cover to the car.

N26 only: what BMW changed for SULEV

IAIK says the N26's SULEV differences concentrate on containing hydrocarbon emissions rather than on creating a different performance category. BMW's training says the N26 was the first turbocharged SULEV gasoline engine worldwide that needs no secondary air system. IAIK says a generic secondary-air inspection checklist should not be applied to the N26.

The airbox has an additional hydrocarbon filter in its upper half, which BMW's training says is replaced with the airbox as a complete unit if damaged, and the vacuum reservoir is no longer built into the engine cover. The high-pressure fuel pump has a laser-cut groove in its outlet valve so that residual rail pressure falls more quickly after shutdown, which reduces leakage risk. The HDEV5.2 solenoid injectors are hand-selected after leak testing to less than 0.5 mm³ per minute at 20 MPa (200 bar). IAIK calls that a manufacturing selection criterion, not a home diagnostic test or permission to substitute an N20 injector.

BMW's training lists other N26-specific hardware: a stainless corrugated fuel line from the engine compartment to the high-pressure pump, a close-coupled catalytic converter with a 900-cell first monolith where the N20 uses 600 cells, and a radiator coated to convert ozone. IAIK says to match current part numbers and supersessions to the vehicle, because physical similarity to N20 hardware is not enough evidence of interchangeability.

Technician service notes

N20: the Valvetronic servomotor can be fitted with its oil spray nozzle missing. The N26 valvetrain is the same as the N20's. The small clip-in nozzle lubricates the worm-drive gearing. During the relevant assembly work, confirm that it is present, correctly positioned and fully engaged. BMW's training warns that an incorrectly engaged nozzle can vibrate and break. IAIK says this is an assembly check when the parts are disturbed, not a scheduled instruction to take apart a working Valvetronic system.
N20: the engine control unit sits on an aluminium heat-sink plate at the intake manifold, cooled by intake airflow, and BMW's training says correct mounting and good level contact are part of the heat-transfer path. BMW's training also says not to try control units from other cars as a test, because an immobilizer adjustment cannot be reversed.
Both engines: BMW's training says a removed coolant pump that will be reused should be set down still filled with coolant, because drying out may make the bearings stick. The N26 cooling system is the same as the N20's. The training also says to turn the pump impeller by hand to confirm it moves freely before installation. IAIK says this is storage and reinstallation care, not an instruction to replace every working pump.
N20: BMW's training says to remove the ignition coils and cover the spark plugs before any change to the fuel system, and that coils heavily saturated with fuel must be replaced. It says sustained contact with fuel reduces the insulating resistance of the coil silicone and can cause arcing and misfires. The high-pressure fuel system is not to be opened until the coolant temperature is below 40 °C (104 °F), and cleanliness and the repair sequence still apply after cooling.
N20: in BMW's N20 training the vacuum reservoir for the wastegate is built into the engine cover, and the training says to disconnect the vacuum line before removing the cover or damage may result. On the N26 the vacuum reservoir is no longer built into the engine cover.
Both engines: BMW's training says the solenoid injector stems are fragile, that they can only withstand 6 Nm of torque, and that the special removal tool must be used or the injectors will be damaged.

Known Failure Points and Service Items

Recall information on this page was checked against NHTSA on October 1, 2026. Recalls are added and closed over time, and whether a specific car is covered is a VIN check with BMW or NHTSA.

01 Timing chain and oil pump drive chain (both engines)

IAIK says chain and guide condition is an important N20 and N26 buying check. Because the camshaft drive and the lower oil-pump drive are separate, IAIK says an inspection should distinguish them and establish whether debris has entered the oil system.

IAIK sees the timing chain often on N20s in our shop.

BMW's bulletin SI B11 03 17 (revision 10, October 2021) extends the limited warranty on the timing chain and oil pump drive chain modules to 7 years or 70,000 miles from the original in-service date, for defects in materials or workmanship. It lists N20 and N26 cars from model years 2012 to 2015 in the E84 X1, E89 Z4, F10 528i, F22 and F23 2 Series, F25 X3, F26 X4, and F30, F31, F32, F33, F34 and F36 models, with production dates that end no later than February 28, 2015. BMW calls it a warranty extension, not a recall or service action, and says no immediate repair is needed unless the car is having a chain problem. BMW says the model list is informational and not the only deciding factor for eligibility. BMW records eligibility against the VIN, so the VIN, not the model name, settles coverage. Because the coverage runs from the original in-service date, check the VIN with BMW instead of assuming any coverage remains.

The concern BMW describes is a whining noise from the lower engine area near the oil pump that rises in frequency with engine speed. BMW gives excessive wear of the timing chain and/or the oil pump drive chain as the cause. When its diagnosis calls for it, BMW's repair replaces the oil pump drive chain module, the timing chain, the chain tensioner, and the slide, tensioning and guide rails. BMW's diagnosis uses two measured checks, a timing chain elongation check and an oil pump drive chain frequency check. BMW's case checklist for a chain complaint also asks whether the oil filter holds metal or plastic debris and whether the chain guides look damaged when viewed through the oil filler opening. IAIK says a view through the filler opening does not replace the engine-specific chain assessment.

BMW's October 2017 revision of the bulletin names these repair parts: oil pump drive chain module 11 41 7 605 366, timing chain 11 31 8 648 732, chain tensioner and guide rail 11 31 7 592 877, sprocket 11 31 7 603 944, slide rail 11 31 7 592 850 and chain tensioner with gasket ring 11 31 8 685 091. The parts catalog lists all six as current numbers for these engines. BMW's October 2021 revision instead lists one kit, 11 31 5 A19 AA2, containing the oil pump drive chain, timing chain, tensioner and guide rail, crankshaft sprocket, slide rail and chain tensioner with gasket ring. The parts catalog shows the chain tensioner 11 31 7 567 680 replaced by 11 31 8 685 091 in December 2016, so ask which revision was fitted.

BMW also published SI B11 02 21 (revision 4, September 2021), which describes repair benefits under a class action settlement for the same chain modules on N20 and N26 cars built through February 2015. The bulletin states that BMW denies any wrongdoing, and that the benefit is limited by vehicle age and mileage and by the terms of the settlement. This guide does not state whether any of these programs still applies to a given car.

Watch for a whining noise from the lower engine area near the oil pump that rises with engine speed, abnormal chain noise, metal or plastic debris in the oil filter, and chain guides that look damaged through the oil filler opening. Ask the seller's invoice to separate timing-chain work from oil-pump-drive work and to say what was inspected or replaced. IAIK does not establish a universal replacement mileage or justify ordering every chain component solely from an engine badge.

02 Coolant pump plug connector, recall 24V-608 (both engines)

BMW recall 24V-608, filed August 13, 2024, covers certain model year 2012-2018 BMW models with the N20 or N26 engine. The model years in BMW's filing are:

X1 sDrive28i and xDrive28i, 2012-2015
Z4 sDrive28i, 2012-2016
528i and 528i xDrive, 2012-2016
X5 xDrive40e, 2016-2018
2 Series Coupe (228i, 228xi), 2014-2016
2 Series Convertible (228i, 228xi), 2015-2016
X3 sDrive28i and xDrive28i, 2013-2017
X4 xDrive28i, 2015-2018
3 Series Sedan (328i, 328xi), 2012-2016
3 Series Sportswagon (328i, 328xi), 2014-2015
4 Series Coupe (428i, 428i xDrive), 2014-2016
4 Series Convertible (428i, 428i xDrive), 2014-2016
328xi Gran Turismo, 2014-2016
4 Series Gran Coupe (428i, 428xi), 2015-2016

BMW's filing describes the cause as blow-by liquid from the crankcase ventilation system collecting on the intake air hose and dripping onto the pump's plug connector; over time this could lead to fluid getting into the plug, a short circuit and, in rare cases, a fire. BMW's remedy is to inspect the pump's socket and plug connector for fluid and corrosion, repair or replace parts as needed, and fit a splash protection cap. BMW's bulletin says the electric coolant pump itself has not been recalled. NHTSA's record says the remedy is free of charge and that owner notification letters were mailed on March 28, 2025.

BMW's filing lists pump part numbers ending 8625097, 8635089 and 7604027. The parts catalog lists 11 51 8 635 089 as the current electric coolant pump for these engines and shows 11 51 7 604 027 replaced by it in March 2015.

Watch for fluid or corrosion at the pump's plug and socket, and for an open recall on the VIN. BMW's filing does not report a driver warning for this condition, so the VIN check matters more than any symptom. BMW's FAQ points owners to bmwusa.com/recall for current status.

03 Brake vacuum pump lubrication, recalls 13V-454 and 14V-627 (both engines, early builds)

BMW recall 13V-454 (2013) and its expansion 14V-627 (2014) cover the engine vacuum pump that supplies brake power assistance, which can fail from insufficient lubrication. NHTSA's summary for 13V-454 names certain 2012-2014 320i, 328i, 320i xDrive and 328i xDrive sedans, 2014 328i xDrive Sports Wagons, 2012-2013 528i and 528i xDrive sedans, 2013-2014 X1 sDrive28i and xDrive28i, and 2012-2014 Z4 sDrive28i roadsters. NHTSA's summary for the 14V-627 expansion also names 2013-2014 X3 xDrive28i and 2014 428i and 428i xDrive coupes. BMW's bulletin for 14V-627 (SI B11 21 14, December 2014) names N20 and N26 engines produced from May 2012 to August 2013 in the E84 X1, E89 Z4, F10 5 Series, F22 2 Series, F25 X3, F30 and F31 3 Series, F32 4 Series and F34 Gran Turismo models.

BMW describes a defect in the intake camshaft that can reduce oil to the engine vacuum pump, and says pump failure can lead to a loss of power-assisted braking. A failure of the pump reduces braking power, according to NHTSA, which says this could increase the risk of a crash. NHTSA's record for 14V-627 gives the remedy as a locking ring in the camshaft that retains the camshaft seal disk. BMW's bulletin says the intake camshaft is inspected and then either fitted with a spring steel sleeve or replaced. BMW's bulletin says a recall label on the B-pillar with code 666 punched out shows the campaign was already done.

Watch for an open recall on the VIN and for the code 666 label on the B-pillar.

04 Crankcase ventilation and oil consumption (both engines)

BMW's oil consumption bulletin, SI B11 03 13 (all models), says turbocharged engines consume more oil than naturally aspirated engines and that this is normal and not a defect. The bulletin gives up to 1 quart per 750 miles as the consumption specification for BMW engines other than Motorsport. It lists a malfunctioning crankcase ventilation system, external leaks and overfilling among the causes to check before an oil consumption analysis.

Watch for oil consumption that changes sharply between services, external oil leaks, and an oil level above the upper dipstick mark.

05 Spark plugs (N20)

BMW service information records a revised spark plug for the N20 from production date 03/2012. Cars built before 03/2012 carried a shorter plug interval, and BMW allows the longer interval only once the revised plug is in. The parts catalog shows the earlier plugs 12 12 0 038 704 and 12 12 0 038 896 replaced by 12 12 0 039 664.

Watch for the plug interval and plug part number in the service record on any N20 built before 03/2012.

06 Oil filter housing, valve cover gasket and oil pan leaks (IAIK, shop experience)

IAIK sees oil filter housing problems, valve cover gasket leaks and oil pan leaks on N20s in our shop. IAIK gives no frequency or mileage for them.

07 Stripped oil pans and drain plugs (IAIK, shop experience)

IAIK sees stripped oil pans and drain plugs on N20s in our shop, from over-tightening on the versions with a plastic drain plug and a plastic pan.

BMW's repair data lists a plastic oil pan with a plastic drain plug on N20 and N26 cars without all-wheel drive, tightened to 8 Nm with a new plug, while all-wheel-drive cars use an aluminum pan whose drain plug takes 25 Nm with a new sealing ring.

08 Valvetronic and injector issues (IAIK, shop experience)

IAIK sees Valvetronic issues and injector issues on N20s in our shop. IAIK does not give a frequency or a mileage for them.

Reliability Verdict

IAIK does not give a reliability rating for either engine. What IAIK does say is that chain and guide condition is an important buying check, and that the N26's emissions-specific components deserve separate inspection. BMW's own documents point at the same drive chains and add two other documented items: the coolant pump plug connector under recall 24V-608, and the brake vacuum pump on early builds under recalls 13V-454 and 14V-627.

IAIK does not establish a universal chain replacement mileage. IAIK's test is the record: chain work, cooling-system condition, oil leaks and any diagnosed ventilation or fuel-system faults.

From our own shop, IAIK adds the items it sees on N20s beyond the timing chain: oil filter housing problems, Valvetronic and injector issues, valve cover gasket and oil pan leaks, and stripped oil pans or drain plugs from over-tightening. IAIK gives these as shop experience, not as a rating.

Power Potential

Not established by IAIK; the dossier gives no tuning ranges and this guide does not estimate any. The factory rating in BMW's training is 240 hp and 350 Nm for both engines, with a 7,000 rpm cutoff.