Oil landing on a hot exhaust burns off long before it can reach the floor, which is why plenty of owners get the smell for months and never see a mark. When something does finally land on your lot, it has usually come from one of two parts. Which of the two it is gets answered with the car in the air and a torch on the joint, not from a description.
Each one of these points at a different part of the engine, and one of them is not purely an oil problem at all once you look properly. Tell us which version you have and we can narrow it down before the car even arrives.
You step out at the carpark and there it is, something like an iron left face down on a shirt. That is oil reaching the exhaust manifold or the turbo housing and cooking off on contact, and on these engines the valve cover joint sits almost directly above both. Nothing gets as far as the concrete, so owners live with it for months. It is also the version that matters most, because oil on glowing metal is how bonnet fires start.
Tell us when the smell shows up → 02Something dark on the concrete, usually toward the middle of the car rather than under the nose. Oil that escapes at the top of a BMW engine does not fall straight down. It tracks along the block, picks up the gearbox seam or a wiring loom on the way, then lets go at the lowest point it can reach. Photograph where it sits relative to the wheels and a couple of candidates are already out.
Send the photo across → 03This one catches owners out on the fours and the sixes alike. On the B48 the housing itself carries coolant, and on the earlier engines a factory oil cooler on the housing puts coolant through the same part where one is fitted. Either way a set of seals is all that holds the two apart, and the joint can let go on the oil side, the coolant side or both. Two levels falling at once reads like two faults and two bills, and often it is one part behind both. Look in the expansion bottle before you assume what you have is only an oil leak.
Both levels dropping? Message us →Take the four-cylinder cars first. On the N20 and the B48, the crankcase breathing gear lives inside the valve cover rather than bolted on beside it. There is a thin diaphragm and a pressure regulator sitting in there, and when that diaphragm splits the engine starts pulling on its own crankcase instead of venting it. Oil then gets pushed out past seals that were perfectly healthy the week before. Fitting a fresh gasket to a car in that state changes nothing at all, which is why we want to know how the breather is behaving before any part is ordered.
The oil filter housing is the other half of it. On the B48 that part is a plastic moulding; on the N20 and on the N52 and N55 sixes it is an aluminium casting, where the plastic piece that ages is the screw-on filter cap up top. Where a factory oil cooler is fitted to the housing, oil and coolant run through the same part with only a set of seals holding them apart. That is how any of these engines can drop coolant and oil together and still need one gasket set rather than two repairs. Where they differ is in how they fail. Plastic goes brittle and splits at the bolt bosses, while on the sixes the joint between casting and block hardens until it stops sealing, and what escapes there runs down the side of the engine onto everything below.
Our weather earns some of the blame. Underbonnet temperatures stay high, traffic here means plenty of heat with very little airflow through the bay, and rubber that spends years going through those cycles stops springing back. Plastic ages differently. It does not soften, it goes brittle, then cracks at the bolt bosses where it is clamped hardest.
One last thing worth saying out loud. An engine that has been quietly losing oil for a year has a second problem coming, because that same oil is what the timing chain guides depend on. If yours is an N20 and you have heard anything rattly on a cold start, our N20 timing chain page is the one to read next. Otherwise the general oil leak page sets out the hunt without a badge attached, and the BMW page has the rest of what we take on for these cars.
BMW talks in engine codes far more than model names, and once you have yours the search area shrinks to something manageable. Find your model and year below, then read across. Where two rows overlap on years, the code in brackets is the one printed on your registration papers and it settles which line belongs to you.
One overlap the bracket codes cannot settle on their own: an F30 320i registered in 2015 or 2016 left the factory with either the N20 or the B48 depending on when it was built, so both rows will look like yours. Send us the registration year and the chassis number and we will tell you which of the two is actually in the car. Not certain which engine you have at all? Same message, same answer. Two further notes on the table above. The N26 is the same engine as the N20 under a different emissions specification, so that row reads the same for both. And a car that has been sitting on a leak for years often has more than one of these live at the same time, which is why the order we tackle them in matters as much as the list itself.
On the four-cylinder cars especially, these two jobs get written down using the same handful of words and they are not the same work at all. Getting it the wrong way round is how an owner ends up paying twice.
Choosing between them is not guesswork. The cover only comes into view once the engine cover, the intake pipework and whatever else BMW has stacked above it are out of the way, and by that point we can see whether oil is escaping past the gasket line or arriving from somewhere it has no business being. You get told which of the two it is with the photographs sitting in front of you. If the answer is the cheap one, that is what goes on the invoice, and there is nothing bolted onto the end of it.
Smell, mark, or a level that keeps dropping. Which of the three arrived first tells us roughly how high up the engine to begin, and it costs you one message.
Level, colour, and what the filler cap looks like on the underside. A car that has been running low or long overdue changes what we go hunting for, and it changes what we say about the chain guides too.
The engine cover and the pipework across the top come away, then the valve cover area and the side of the block are degreased and dried. Old oil hides a live leak completely.
Seals that look fine on a cold engine will weep once the oil thins out, so the inspection that settles anything happens warm, with the car on the hoist and a light on the joint.
Before a valve cover gasket gets ordered for an N20 or a B48, we want to know the breather inside that cover is still doing its job. Where it is not, the gasket was never the fault to begin with.
Parts and labour listed apart from each other against your own photographs. After the job the area is washed again and the car returns so we can both see it has stayed dry. Old parts travel home in the boot.
You will not find a figure anywhere here, and that is deliberate. Two cars can turn up with the same complaint, the same engine and the same smell, then leave with invoices nowhere near each other. These are the things that decide which end you land on.
A rubber seal and a moulded assembly with a breather inside it are very different parts. The hours are broadly similar. The parts line is not, and that is where owners get caught out.
A housing with no cooler in it wants its gasket and a properly cleaned face, and little else. One with the oil cooler built in means coolant drained, refilled and bled afterwards, and that is real time on the clock.
A four-cylinder has an engine cover and some pipework in the way. A six has more, and a turbo six more again. Access is usually the single biggest line on a job like this.
The valve cover sits above the filter housing, so oil from up top soaks the one below and makes it look guilty. Working out which is actually leaking, and in what order, changes the whole plan.
Years of oil rots the rubber it lands on. Mounts, bushes and hoses under a long-running drip often want doing at the same time, and that is a conversation we would rather have with you upfront.
Degreasing what the leak has coated, and having the car back later to confirm the area stayed dry, both sit inside the job here. Neither turns up as a line you were not expecting.
No part gets ordered and no spanner moves until an itemised quote is in your hands, parts on one line, labour on another, with photographs of your own engine sitting next to both. If the top end comes apart and the picture is worse than the photographs suggested, work stops there and we ring you rather than quietly adding it to the total. Whatever comes off the car goes home with you, and the follow-up check is in the diary before you drive out.
Heat and age, working on the parts that were always going to give up first. The valve cover gasket seals a long thin joint right at the top of the engine, and years of heat cycling harden it until it stops pressing back against the metal. The oil filter housing gasket does a similar job on the side of the block. On top of that, a lot of these parts are plastic. The valve cover is plastic on all four engines. The oil filter housing is plastic on the B48; the N20 and the N52 and N55 sixes use an aluminium casting, where the plastic part is the screw-on filter cap. Plastic does not soften with age the way rubber does, it goes brittle and cracks, usually around the bolt points where it is clamped hardest. Our weather shortens that whole timeline, because an engine bay here lives hot and damp with barely any airflow moving through it in traffic.
We do not put figures on a page, because the same three words on a job sheet cover work that is hours apart. What moves it is which part it turns out to be, since a valve cover gasket is a seal while a valve cover with a failed breather inside it is a whole assembly. Then it is the housing, because one with coolant running through it means the cooling system comes out and goes back in properly afterwards. Then it is access, which on a six-cylinder turbo car is most of the labour on its own. Bring the car in, let us look at it warm, and you get an itemised quote with your own photographs attached before a single part is ordered.
It depends entirely on where the oil is landing. On these engines a lot of it drips onto the exhaust manifold or the turbo, and hot metal plus oil is how an engine bay catches fire, so a strong burning smell is not something to sit on for a fortnight. The quieter risk is the level. A leak can empty a sump faster than you think to check it, and bearings take damage long before a warning light appears. Pull the dipstick before you go anywhere. Anything reading under the minimum mark means the car should be lifted rather than driven, ours included, so message us and we will get a truck to it.
Because the oil never gets that far down. On a BMW four or six the exhaust manifold runs along the side of the head, more or less directly under the valve cover joint, so anything escaping there lands on metal hot enough to burn it off within seconds. What reaches you is the smell through the vents and now and then a wisp of smoke from the bonnet shut line after you park. There is nothing left over to drip. That is why checking the floor misses this one completely, and why a car with no mark at all can still be losing oil steadily.
The N20 four from roughly 2011 to 2016 is the one with the reputation, valve cover and oil filter housing gasket both. The N52 and N55 sixes carry the same pair of weak points, and on those the leak announces itself as smoke or smell off the exhaust manifold rather than as a puddle. The B48 that followed the N20 is the better engine overall, though its oil filter housing is still worth knowing about. The B48 housing carries coolant as standard, and on the earlier engines a factory oil cooler on the housing brings coolant into the picture where fitted. None of that means your car has a problem. There are plenty of dry examples of all four still running around here, so treat the list as a starting point for the search rather than a diagnosis.
Not necessarily, and more often than not it is one fault behind both. Where a factory oil cooler sits on the housing, oil and coolant run through the same part with seals in between, and on the B48 the housing itself carries coolant as standard. When those seals go you can lose oil, or coolant, or both, and on a bad one the two find each other. Check the expansion bottle and the dipstick together, and have a look at what is sitting on the underside of the oil cap while you are in there. Bring us both readings and we will know where to start.
No. Singapore’s Competition and Consumer Commission had the authorised car dealers drop the warranty terms that tied servicing to their own workshops, so a claim cannot be refused simply because an independent did the work. Cover stands as long as compatible parts are used and the manufacturer’s procedures are followed. We do both, and the written report is your record of it. There is more in our piece on servicing under warranty in Singapore.
A valve cover gasket on a four-cylinder is comfortably a day once we know that is the job in front of us. A whole cover is the same labour with a longer wait attached if the part is not sitting on a shelf here. An oil filter housing gasket runs longer on the sixes because of what has to come off above it, and longer again where coolant has to be drained and put back properly. If two things are leaking and we have agreed to deal with the worst one first, you will be back for a look after a couple of weeks of normal driving. Whatever the timeline works out to, it goes in writing alongside the quote.
Timing chains, cooling, the electronics, gearbox work and servicing set up for the way cars get used here, plus the models we take in.
Open the BMW page →The same hunt written without a badge attached: why cleaning comes before looking, what a tracer adds, and how to tell one fluid from another.
See the general method →If your BMW has been running low or long on its oil, the chain guides are the next thing worth listening for. What that noise is, and what it means.
Read the N20 chain page →