Best Engine Oil for BMW 1 Series F40 118i (B38 1.5 Turbo, 140 hp)

The BMW 1 Series F40, launched in 2019, marked a bold departure from every previous generation of the car: for the first time, the 1 Series moved from rear-wheel drive to a front-wheel-drive platform shared with the MINI Countryman and the BMW 2 Series Active Tourer. That shift was controversial among enthusiasts, but it allowed BMW to fit a far more practical interior within the same exterior footprint.

At the heart of the 118i sits the B38A15M1 — a 1.5-litre turbocharged three-cylinder engine producing 140 hp and 220 Nm of torque. This compact unit is part of BMW’s modular engine family, where a single cylinder module is shared across three-, four-, and six-cylinder variants. The same fundamental block is found under the bonnet of the MINI Cooper S and the BMW 216i. Choosing the right engine oil for this unit matters more than many owners realise: the B38 has specific lubrication requirements tied to a strict BMW norm, and cutting corners here can lead to costly consequences.

Quick Answer: Recommended Oil

• Primary specification: BMW LL-17 FE+, ACEA C5, 0W-30
• Alternative viscosity: 5W-30 (must still carry BMW LL-17 FE+ approval)
• Oil capacity (drain and refill): 4.0 litres
• Oil capacity (with filter replacement): 4.25 litres

Always verify the oil carries the BMW LL-17 FE+ approval printed on the bottle — not just “suitable for” or “compatible with” claims.

The B38 Three-Cylinder Engine

The B38 is a technically sophisticated unit that punches well above its displacement. BMW engineers achieved 140 hp from just 1.5 litres by combining a twin-scroll turbocharger with Valvetronic variable valve lift, double-VANOS variable camshaft timing on both intake and exhaust, and high-pressure direct fuel injection (up to 200 bar).

The twin-scroll turbo splits exhaust pulses between two separate channels feeding the turbine wheel. This reduces turbo lag significantly and allows the engine to build boost pressure very early in the rev range — most of the 220 Nm torque figure is available from just 1,250 rpm. For daily driving, this makes the 118i feel considerably more responsive than its three-cylinder configuration might suggest.

Being a three-cylinder, the B38 has an inherent primary imbalance that BMW counters with a single balance shaft running at twice engine speed. The result is a smooth idle and acceptable refinement, though a faint three-cylinder thrum is still audible at certain loads — this is entirely normal.

The F40 118i also features a Gasoline Particulate Filter (GPF) as standard, a requirement introduced under Euro 6d-temp emissions legislation. This has a minor effect on back-pressure but does not change the oil specification requirements.

Understanding BMW LL-17 FE+ Oil Specification

BMW introduced the LL-17 FE+ norm specifically for engines designed to meet the most stringent real-world emissions targets, including those fitted with GPF systems. It supersedes the older LL-04 norm in low-friction, fuel-economy-critical applications, and the two norms are not interchangeable in this engine.

LL-17 FE+ is based on the ACEA C5 sequence, which mandates a High-Temperature High-Shear (HTHS) viscosity of between 2.6 and 2.9 mPa·s. This is lower than the ACEA C3 oils used in older BMW engines (HTHS ≥ 3.5 mPa·s). The reduced HTHS viscosity means the oil film is thinner under extreme heat and shear — exactly the condition needed to reduce internal friction, lower fuel consumption, and cut CO₂ emissions.

LL-04 oils (which many BMW owners are familiar with from older models) must not be used in the B38A15M1. LL-04 is ACEA C3, with a higher HTHS viscosity that would increase friction and reduce fuel economy in this engine — but more critically, it does not meet the additive package requirements of the B38’s lubrication system.

5W-30 as an alternative: A 5W-30 oil carrying BMW LL-17 FE+ approval is an acceptable substitute, particularly in colder climates where the slightly higher cold-start viscosity may be preferred. The 0W-30 grade remains the factory recommendation and provides the lowest cold-start drag.

BMW’s Long Life service intervals (up to 30,000 km or two years under ideal conditions) depend entirely on using oil that meets the full LL-17 FE+ specification. Non-approved oils will void the condition-based service interval and should be changed at 10,000–15,000 km instead.

Technical Specifications

Oil Change Intervals

BMW’s Condition Based Service (CBS) system monitors driving patterns, temperatures, and distance to calculate the optimal oil change interval. Under ideal conditions, the system may extend intervals to 30,000 km or 24 months — but this is only valid with a certified BMW LL-17 FE+ oil.

In practice, many independent mechanics and enthusiast forums recommend shorter intervals of 15,000–20,000 km for vehicles used in urban driving, short journeys, or high-temperature climates. Frequent cold starts, stop-start traffic, and short trips all cause oil to degrade faster than the CBS algorithm fully accounts for. If your 1 Series spends a lot of time in city traffic, erring on the side of 12,000–15,000 km intervals is sensible.

Always replace the oil filter at every oil change. For the B38, the filter housing is located on top of the engine and is straightforward to access.

Common B38 Problems Related to Oil

Timing Chain Wear

The B38 timing chain has attracted attention in owner forums and specialist workshops. The chain drives the inlet and exhaust camshafts and relies entirely on pressurised oil flow for lubrication and tensioner function. Owners of higher-mileage B38 engines have reported a rattling or chattering noise on cold starts, particularly in the first few seconds before oil pressure builds — a classic sign of chain stretch or tensioner wear.

Neglected oil changes, low oil levels, or use of non-approved oil accelerates wear on the chain guide rails and tensioner. If a cold-start chain rattle is present, the issue should be investigated promptly; continued driving risks the chain jumping a tooth, which will cause misfires, and in severe cases the chain can fail catastrophically.

Elevated Oil Consumption

Some B38 engines have exhibited higher-than-expected oil consumption, particularly in the first 20,000–30,000 km of life as piston rings bed in. BMW considers up to 0.5 litres per 1,000 km acceptable during this period. If consumption remains high beyond break-in mileage — or suddenly increases on a higher-mileage engine — it can indicate worn valve stem seals or piston ring wear.

Check the oil level every 3,000–4,000 km. Top up only with oil matching the BMW LL-17 FE+ specification; mixing non-approved top-up oil with the correct base oil dilutes the additive package and undermines the lubrication system’s performance.

Carbon Buildup on Intake Valves

Because the B38 uses direct injection exclusively (fuel is injected into the cylinder, not the intake port), the backs of the intake valves are never washed with fuel. Over time, oil vapour recirculated through the crankcase ventilation system deposits carbon on the valve heads. Symptoms include a rough idle, hesitation at part-throttle, and reduced power. Carbon cleaning via walnut blasting is typically recommended around 80,000–100,000 km.

Conclusion

The BMW 1 Series F40 118i B38A15M1 is an efficient and well-engineered engine that rewards careful maintenance. The single most important decision you make for this engine is oil specification: BMW LL-17 FE+ is mandatory, and the 0W-30 viscosity grade delivers the low friction and fuel economy the engine is designed around. Use only approved oil, change it at appropriate intervals (no longer than 15,000–20,000 km in typical UK use), and monitor the oil level regularly given the B38’s known tendency for modest consumption. Do these things consistently, and this three-cylinder unit will prove durable and trouble-free.

Sources:

• A Deep Dive into BMW B38 Engine Issues and Maintenance Tips | Orbi Motors
• Exploring Timing Chain Issues in the BMW B38 Engine: A Guide
• Understanding BMW B38 Engine Problems and Their Impact

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