BMW Oil Filter Housing Gasket Leak (OFHG): N52 / N54 / N55 / N20 UK Guide
The BMW oil filter housing gasket (OFHG) leak is one of the most common oil leaks across the modern BMW range, affecting the N52 and N53 sixes, the N54 and N55 turbo sixes, and the N20 and N26 four-cylinders. The oil filter housing bolts to the side of the engine and its gasket hardens with heat and age; when it fails, engine oil weeps out, typically running down onto the accessory / serpentine belt, and on the N20 and N26 it can also let oil and coolant mix inside the integrated cooler. It looks alarming but is usually a cheap, well-understood repair. This guide explains how to spot it and what it should cost.
Quick answer
The oil filter housing gasket is a common, low-cost oil leak, typically £150 to £450 at an independent specialist. The classic sign is oil weeping down the side of the engine onto the drive belt. On the N20 and N26 the housing also carries an oil-to-coolant cooler, so a failed gasket there can mix oil and coolant. Left long enough, oil soaks the belt (which can then fail), so it is worth fixing promptly rather than because it is catastrophic in itself.
What causes the problem?
The oil filter housing is an aluminium casting bolted to the side of the engine block that holds the oil filter and, on many engines, routes oil through a cooler. It is sealed to the block by a gasket (an O-ring or a profiled seal depending on engine). That gasket sits in a hot, heat-cycling location and hardens and shrinks over time, losing its seal, so pressurised engine oil weeps out of the joint. On the naturally aspirated N52 / N53 and the turbo N54 / N55, the leak is oil-only and usually runs down the side of the block onto the accessory belt and pulleys. On the N20 and N26, the housing integrates an oil-to-coolant heat exchanger, so a failed gasket can allow oil and coolant to mix, showing as a milky residue or cross-contamination in either system. The repair is to remove the housing, replace the gasket (and inspect the belt if it is oil-soaked), which is straightforward on most of these engines.
Symptoms, what to listen and look for
- Oil weeping or dripping down the side of the engine block, often visible above and behind the accessory belt.
- Oil on the serpentine / drive belt, tensioner or pulleys, or an oil-soaked, glazed or cracking belt.
- Burning-oil smell after a drive as leaked oil contacts hot exhaust or engine parts.
- Slowly dropping oil level between services with no visible smoke.
- On the N20 / N26: milky oil, an oily film in the coolant, or coolant contamination from the integrated cooler.
- Oil spots on the driveway or garage floor under the front of the engine.
- Low oil level warning in more advanced cases.
Affected BMW models
| Year | Badge | Chassis | ULEZ | Notes |
|---|---|---|---|---|
| 2005-2011 | 325i / 328i / 330i (N52 / N53) | E90 / E91 / E92 | Yes (Euro 4 petrol) | Very common host; oil-only leak onto the belt |
| 2007-2013 | 335i (N54) / 335i (N55) | E90 / E92 / F30 | Yes | Turbo six; oil-only OFHG leak |
| 2010-2016 | 528i / 535i (N20 / N55) | F10 / F11 | Yes | 5 Series; N20 four and N55 six both affected |
| 2012-2016 | 320i / 328i (N20) | F30 / F31 | Yes | N20 four-cylinder; housing carries the oil-to-coolant cooler |
| 2012-2016 | X3 20i / 28i (N20) | F25 | Yes | N20 SUV application; check for oil / coolant mixing |
| 2014-2018 | X1 / 220i / 320i (N20 / B48 era) | F48 / F22 / F30 | Yes | Late N20 cars; same OFHG design |
| 2012-2016 | 328i (N26 SULEV) | F30 | Yes | N26 is the low-emission N20 variant; rare in the UK, mostly US imports |
UK repair-cost exposure
Indicative UK figures for 2026. Real costs vary by region, specialist, parts supply, and labour rates.
| Scenario | Indie BMW specialist | BMW main dealer | Notes |
|---|---|---|---|
| Oil filter housing gasket replacement at independent specialist | £150 - £450 | £450 - £750 | Gasket / O-ring and labour; straightforward on most of these engines. |
| OFHG plus oil-soaked accessory belt and tensioner renewal | £300 - £650 | £650 - £1,000 | If the leak has contaminated the belt, it is replaced at the same time. |
| N20 / N26: gasket plus coolant flush after oil / coolant mixing | £350 - £700 | £700 - £1,100 | Adds a cooling-system flush where the integrated cooler has cross-contaminated. |
| Consequential repair after a snapped oil-soaked belt | £500 - £1,500 | £1,000 - £2,500 | Rare; if a belt failed and debris or a lost belt caused further damage. |
What evidence should a buyer ask for?
- Look down the side of the engine block at viewing for oil weeping above the accessory belt.
- Inspect the serpentine belt and pulleys for oil contamination, glazing or cracking.
- Check the oil level and look for any milky residue on the oil cap or in the coolant (N20 / N26 especially).
- Ask for any invoice showing the oil filter housing gasket has already been replaced, dated and with mileage.
- Smell for burning oil after the test drive and check for fresh oil spots where the car was parked.
- On N20 / N26 cars, inspect the coolant for an oily film that would indicate the integrated cooler is cross-contaminating.
- Confirm recent oil-service history so a slowly dropping level can be attributed to the leak rather than consumption.
Buy, negotiate, or walk away
Buy
No visible oil weep down the block, a clean dry accessory belt, correct oil level, clean coolant with no milky residue, and ideally a documented OFHG replacement if the car is older or higher mileage.
Negotiate
A visible oil weep onto the belt with no repair history. Use £150 to £450 as the negotiation floor, more if the belt is oil-soaked and needs replacing at the same time.
Walk away
Milky oil or oil in the coolant on an N20 / N26 that has not been investigated (possible cooler cross-contamination or, separately, a head-gasket concern), or a heavily oil-soaked belt on the verge of failure with no acknowledgement from the seller.
Long-term ownership verdict
The oil filter housing gasket is a routine ageing leak rather than a design flaw with serious consequences, and once replaced it is typically good for many years. The only reason to treat it promptly is the knock-on risk of oil soaking the accessory belt, which can then fail. On the N20 and N26 it deserves a closer look because the integrated oil-to-coolant cooler means a failed gasket can mix the two fluids. Across the whole family it is one of the cheaper items on the list and should not put you off an otherwise-good car, but it is an easy, honest negotiation point at viewing.
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Frequently asked questions
What is the BMW oil filter housing gasket (OFHG) leak?
The oil filter housing bolts to the side of the engine and is sealed to the block by a gasket. That gasket hardens and shrinks with heat and age, so pressurised engine oil weeps out of the joint, usually running down the side of the block onto the accessory belt. It is one of the most common oil leaks across the N52, N53, N54, N55, N20 and N26 engines, and is a cheap, well-understood repair.
How much does it cost to fix an OFHG leak in the UK?
£150 to £450 at an independent BMW specialist for the gasket and labour; £450 to £750 at a main dealer. If the leak has soaked the accessory belt, that is replaced at the same time and the bill rises to £300 to £650. On the N20 and N26, a cooling-system flush may be added if oil and coolant have mixed.
Why does the OFHG leak matter if it is just a small oil weep?
In itself it is not catastrophic, but the oil tends to run onto the serpentine / accessory belt. An oil-soaked belt degrades and can eventually fail, which loses your water pump, alternator and power steering drive and can cause further damage. That downstream risk, not the leak itself, is why it is worth fixing promptly rather than ignoring.
Can the oil filter housing gasket mix oil and coolant?
On the N20 and N26 it can. On those engines the housing integrates an oil-to-coolant heat exchanger, so a failed gasket can let oil and coolant cross over, showing as milky oil or an oily film in the coolant. On the naturally aspirated N52 / N53 and the turbo N54 / N55 the leak is oil-only and simply weeps out onto the block and belt.
How do I check for an OFHG leak when viewing a car?
Look down the side of the engine block above the accessory belt for oil weeping or dripping, and inspect the belt and pulleys for oil contamination or glazing. Check the oil level, and on N20 / N26 cars look at the oil cap and coolant for any milky residue. A burning-oil smell after a drive and fresh oil spots where the car was parked are supporting signs.
Is the OFHG leak the same as a valve cover or oil pan gasket leak?
No, though they are often confused because all three are common BMW oil leaks. The oil filter housing gasket sits where the filter housing meets the block; the valve cover gasket seals the top of the engine; the oil pan (sump) gasket seals the bottom. Each leaks from a different place, so it is worth identifying which joint is weeping, as the labour and cost differ. The OFHG is usually one of the cheaper of the three.
Should an OFHG leak stop me buying the car?
No. It is a common, cheap, well-understood repair and, on its own, an easy negotiation point rather than a deal-breaker. The only times to look harder are an N20 / N26 with oil and coolant mixing that has not been investigated, or a leak that has already badly contaminated the belt. Otherwise, factor the modest fix into your offer and move on.