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Old 07-07-2017, 04:20 AM   #1
Registered User
Join Date: May 2017
Location: Sydney, Australia
Posts: 2
My Ride: 2003 318i
318i Oil Consumption

Hi everyone,

Currently having a problem with my 2003 318i, which I've only had for about 2 months.

After driving about 1700kms, I generally get a yellow oil light warning and need to top it up by a litre. I am always using 5w-40 LL-01 spec oil for oil change and top ups.

To try and fix this, I've done the following so far:
  • New CCV and hoses
  • New inlet manifold gaskets (done with the CCV of course)
  • New oil filter housing gasket
  • New VANOS solenoid seals

I've also degreased the engine bay, top and bottom, and have found no leaks from the vacuum pump or rocker cover. The only evidence of a leak is around the sump gasket, but the leak seems fairly minor and isn't even leaving a drop of oil on my driveway ever, so I'm fairly convinced this isn't the course of such drastic oil loss.

So I've pretty much accepted that I'm largely leak free and that the missing oil has to be due to oil consumption. It's worth noting that there is no evidence of any smoke form my exhaust that I can see.

I have spoken to a number of mechanics as well as my local dealer and they are recommending I change oil grade. The dealer reckons they use 10w-30 or 10w-40 for e46's that consume oil, and an indy BMW specialist recommends 20w-50 (Liqui Moly). Another mechanic has recommended trying an additive for valve stem seals.

I realise that worn seals or rings are the most likely cause of the problem, but fixing that will be over double what I paid for the car so not really an option right now. Plenty of searching/reading on this and other e46 forums makes it seem like using thicker oil is not actually a good idea, so I'm kind of stuck with what I should be doing.

Other than this problem, the car runs like a dream - no noise, smooth acceleration and no error lights.

Any ideas to help fix or at least slow down the oil consumption. FWIW, I generally do oil change every 7000 to 10000 kilometres.

Cheers and thanks for any help!

EDIT: Engine is N42B20 by the way

Last edited by sqdoof; 07-07-2017 at 04:28 AM. Reason: Forgot to add important engine details
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Old 07-07-2017, 07:22 AM   #2
Registered User
Join Date: Jul 2008
Location: USA
Posts: 6,171
My Ride: 2001 330Ci
You've written that the CCV has been replaced. Is the CCV made by the original supplier to BMW or is it aftermarket? Can you remove the CCV "oil" return line to see if "oil" is, in fact, being returned to the crankcase. I realize your engine is not an M54, so I have to ask if the complete "oil" return path was cleaned. In the M54 the "oil" is returned via the dipstick tube. A blocked "oil" return path can exacerbate oil burning.

I've written "oil" the liquid returned to the crankcase is really a mix of oil and water. I installed an oil catch can in my 330Ci. You wouldn't believe how nasty the "oil" is!!

One way to tell if it's rings or valve seals is to get the car up to speed, let off the gas for a second or so and then press the accelerator. Check the color of the smoke. Blackish smoke indicates oil being sucked into the combustion chambers and being burned.

The other issue could be the oil control rings-they could be carboned up.

Let me explain. The oil control ring, just like the 2 compression rings, sits in a grove in the piston. The order, from the top, is compression ring, compression ring and oil control ring. The oil control ring scavenges oil from the cylinder wall to prevent the oil from being burned. The oil control ring grove has holes that allow oil to return to the crankcase. Those holes have a tendency to narrow over time as the piston, being extremely hot, "cooks" the oil a bit. It's sort of like arterial sclerosis in old folks!! Unfortunately, there's no real way to determine if the oil drain holes are narrowed except for an engine teardown.

So, my recommendations are:
- check the operation of the CCV (I protest that it was designed by an engineer who'd been fired by Audi!) to ensure its doing the job.
- try a different brand of oil. I would not go to a higher viscosity oil as your engine was designed around a specific set of oil parameters. Here in America some folks swear by Shell Rotella T6.
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ccv, consumption, leak, oil, valve stems seals

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