[relative4]

'08 335xi E90 manual, 68K miles. I purchased it at 66K miles 4 months ago and immediately changed the oil with Motul 8100. In the 1500 miles I've driven it since then, I have had to add 2 quarts.
The previous owner didn't have this issue. He didn't drive anywhere near as hard as I do; I'm running MHD stage 1, and I always drive hard.
There is absolutely no leakage anywhere, and I don't see smoke. There must be smoke I don't see, cause it's definitely not leaking. The performance is great, and there are no ugly turbo noises.
Can anyone recommend diagnostic steps? Is this behavior consistent with a PCV problem?
Thanks!

[RayLivingston]

It is either leaking, or burning. If it's burning, the spark plugs will be heavily coated with oil ash after burning so much oil in such a short time.

My money is on leaking. It is NOT always obvious, because they will sometimes leak only when running at speed, and the oil can get largely carried away by the airflow under the car. On what do you base your statement that it is NOT leaking? What steps have you taken to check for leaks?

Most common leak points are valve cover gasket and oil filter block gasket, both very easy to replace (~2 hours and $30 each). Next most likely is the oil pan gasket, which is NOT so easy to replace.

Regards,
Ray L.

[relative4]

I replaced the OFHG proactively immediately on receipt of the car, while I was walnut blasting and replacing the serpentine time bomb. It was not and is not leaking.
I have thoroughly inspected the VCG and it has only the barest hint of seeping. I have a solid basis of comparison in my wife's VCG, which is almost due for replacement.
I have pulled the belly pans several times and thoroughly inspected for any signs of leakage, and there is absolutely nothing. Again, my wife's badly leaking OPG provides me an excellent basis of comparison. Her oil level does not drop significantly.
I have also inspected for leaks from the front and rear main seals, and all is well.
I'll pull plugs for inspection, thanks.

[RayLivingston]

Well, if it absolutely is not leaking, then it's burning. Examining the spark plugs should prove that. If so, you're down to generally bad things, in rough order of increasing PITA to repair:

1) Crankcase breather problem
2) Turbo oil seal leak
3) Valve guide seal leaks
4) Head gasket leak
5) Piston oil control rings worn/clogged/broken

Pray for #1, as it is by FAR the simplest and cheapest to repair.

Regards,
Ray L.

[relative4]

Is that just a matter of replacing the PCV valve on the back of the valve cover? Looking at the Rob Bent version for that.

[RayLivingston]

No. I'm not completely up to speed on the details of the N54 breather system. There is also for certain a pipe that connects the intake manifold to the valve cover (connected near the intake side, rear of the valve cover), and that pipe contains a check-valve. I believe the oil separator is integrated into the N54 valve cover, and contains small passages which become clogged over time, necessitating periodic replacement of the valve cover itself. And, of course, the PCV valve itself is screwed into the valve cover above the #6 intake port.

Regards,
Ray L.

[relative4]

I've been studying the system, and it doesn't look like a problem with either check valve would cause this symptom. For the PCV system to cause this symptom, the separator system in the valve cover would have to lose effectiveness and start passing oil. Such as if the cyclonic separators got clogged?
If the valve cover were the source of this problem, is there any cleaner such as SeaFoam that could be run through the engine to clean the valve cover separator system without removing the valve cover?

[RayLivingston]

I'm not sure how likely a CCV failure is to cause oil consumption on an E90. It is a major problem on E46s. I could imagine a failure of the crankcase pressure regulator in the valve cover causing oil consumption, though that may also require a failure of the check valve in the vacuum pipe.

I'm surprised nobody else has chimed in on this, as excessive oil consumption seems a fairly common complaint....

Regards,
Ray L.

[type-dRew]

I feel like a bit of oil consumption is to be expected with a 10+ year old turbocharged engine.

Mine uses a little but it also leaks a little. So when i fix those leaks I guess i'll see how much consumption is to be expected with old turbos and no leaks.

[RayLivingston]

Originally Posted by type-dRew

I feel like a bit of oil consumption is to be expected with a 10+ year old turbocharged engine.

Mine uses a little but it also leaks a little. So when i fix those leaks I guess i'll see how much consumption is to be expected with old turbos and no leaks.

Two quarts in 1500 miles is WAY more than "a bit of oil". That's even way worse than my '64 Jaguar! My '07 335i with 110K miles burns a quart of oil every 6K miles, which is not much different from my '01 325i when it was that age. Even at 230K miles, the 325i does much better than what we're talking about here.

Regards,
Ray L.

[type-dRew]

Originally Posted by RayLivingston

Two quarts in 1500 miles is WAY more than "a bit of oil". That's even way worse than my '64 Jaguar! My '07 335i with 110K miles burns a quart of oil every 6K miles, which is not much different from my '01 325i when it was that age. Even at 230K miles, the 325i does much better than what we're talking about here.

Regards,
Ray L.

I don't disagree at all. I'm just saying, on an engine I expect to consume some oil and then professed aggressive driving. I'd expect some top offs.

I could go on a twisty canyon run in my old Focus with the Duratec 2.3 engine(non turbo) and by the end of it be nearly a quart low. Those engines just consumed oil, it was part of the deal with aggressive driving.

Not saying his is normal, just saying I wouldn't expect zero consumption.

[tlow98]

what's the weight of this motul 8100?

[relative4]

I'm not a good judge of spark plugs. You guys mind taking a gander at this one?

Outside, no flash:


Inside, no flash:


Inside, with flash:

[RayLivingston]

How many miles on those plugs?

What I see is mostly soot, from rich running. Burning 2 quarts of oil in 1500 miles would have the plugs covered with thick, fluffy, black crud.

https://www.underhoodservice.com/spa...g-diagnostics/

The oil-fouled plug shown in the above link is much worse than I would expect you to find, but still you should see the "fluffly", thick, black/brown deposits.

Did you remove them all? Could be a single cylinder causing your problem.

Regards,
Ray L.

[porsche959]

For what it’s worth, I have a significant valve cover gasket leak on my n52. About a teaspoon or so per day, depending on the weather.

I burn a quart of oil every 700-1000 miles.

I drive very hard - regular redlines and pedal smashing whenever I can.

Sounds like a oil leak to me.

[robthewrench]

Did you pull all the plugs, or only 1? Since that one was dirty, did you replace all of them? If you did you could pull them again in 1000 miles and see the condition.

One other question: How did you measure the amount of oil you needed to add over the 1500 miles? The electronic dipstick is notoriously confusing and it could be quite possible you started a little low, burned <1 qt and are now slightly high.

I would not throw any serious money at this yet, but instead keep monitoring.

[type-dRew]

Aside from color, i'd replace those plugs based on wear also.

It does look clean enough to rule out internal engine issue imo, i'd say it's more than likely a leak combined with regular aggressive driving oil usage.

[dublin14]

FWIW... I was using 2 quarts every 6000km and once I changed to Mannheim syn oil it stopped? Not sure why.

[lowrydr310]

Originally Posted by relative4

The previous owner didn't have this issue.

Do you know the previous owner personally, and know him/her well? If not, that might not be a reliable data point.

I too have an oil consumption issue ,but I have a N52. I know, different engine, but same CCV system. I only have very minor leaks around the oil pan gasket and crank pulley seal; ZERO drips on the ground, but some dampness around the mating surfaces at those points that attracts dust/dirt. I replaced the valve cover gasket (along with valvetronic motor gasket and eccentric shaft sensor gasket) and oil filter housing gasket about 10K miles ago and that made no difference to my oil consumption.

I haven't pulled plugs yet and i haven' t checked for proper operation of the CCV system, specifically the oil separator. I also found no consistency with the rate at which the oil level drops, however one thing I noticed lately is that the consumption seems to increase when most of my driving is long highway drives at consistent speed. I can drive 500-1000 miles in stop and go city driving and don't see the level drop much, but after a few long trips at steady cruising speeds I notice the level will drop. I'm wondering how this relates to the operation of the CCV. I'm thinking that at lower vacuum levels during steady cruising, the membrane in the CCV isn't closing and it's sucking crankcase gases full of oil vapor into the intake.

[Nightmare38oh1]

I’m also going through a quart every 1500-2000 miles. N54 mhd stage 2+. All supporting mods and then some. Just did the ofhg. Have been monitoring since then since it was both a leak and burning. I had the pleasure of my wife driving the car and got to visually see burnt oil coming from the exhaust (blue/white). I’ll also pull plugs again since they are also new within 5000 miles. Car driving normal. No odd turbo noises. Pulls stupid strong.

[tlow98]

Originally Posted by Nightmare38oh1

I’m also going through a quart every 1500-2000 miles. N54 mhd stage 2+. All supporting mods and then some. Just did the ofhg. Have been monitoring since then since it was both a leak and burning. I had the pleasure of my wife driving the car and got to visually see burnt oil coming from the exhaust (blue/white). I’ll also pull plugs again since they are also new within 5000 miles. Car driving normal. No odd turbo noises. Pulls stupid strong.

Sounds like turbo seals, no?

[N54Society]

Oil leak is my guess based on the amount and frequency.