[E92_BGDoc]

It is strange that the oil consumption did not decrease with the valve seals change. Are you sure you installed them correctly? Anyway, from here on i assume you did...

There are three usual ways these engines burn oil unless of course there is a leak somewhere - oil separator, valve stem seals and piston rings/return holes. Since you have taken care of the first two, then there is really one option left and that would require engine tear down. The initial version of N52B25 is well known for its poor oil scraper ring design. As far as i know, BMW changed this in the TU (N52KP) which mostly solved the extreme oil consumption problem. However, in specific cases - combination of the car being used predominantly in congested city traffic and ridiculously long OCI (in EU the usual interval suggested by the BC is 30000km) the oil return holes on the pistons would get blocked and the oil consumption skyrockets. BMW determined this to be due to unfavorable positioning of the return holes and in April 2010 updated pistons were introduced. I think there were pictures of them side by side with the old pistons in a German forum, google it. However, the cost of replacement is quite high and in my opinion not justified.

Anyway, seems like to get any significant improvement you will have to take out the pistons and replace the rings. Not a simple job, but if you can do it yourself then the cost will be low as the components are pretty cheap.

[acmf]

Joining the bandwagon with my N52B25 story.

Started and ran fine, but eventually I got tired of oil consumption that got progressively worse and lately increased to 1l per 1500km. Fixing leaks and replacing valve cover didn't address the issue much.

Decided to bite the bullet and have it checked, hoping that replacing pistons and rings with post-2010 fixed versions would be enough.

No luck.

Rings weren't stuck, but the pistons banged the hell out of cylinder walls beyond any possibility to get them fixed to fit the repair set of pistons and rings. Getting the block sleeved now. At 115000 kms.

[ptpending]

engine block replacement is not so bad thing because if oil is changed at big interval then intake camshaft rod wear it's beds and start to issue funny noises tooo

[n00b0rKa]

Originally Posted by E92_BGDoc

It is strange that the oil consumption did not decrease with the valve seals change. Are you sure you installed them correctly? Anyway, from here on i assume you did...

There are three usual ways these engines burn oil unless of course there is a leak somewhere - oil separator, valve stem seals and piston rings/return holes. Since you have taken care of the first two, then there is really one option left and that would require engine tear down. The initial version of N52B25 is well known for its poor oil scraper ring design. As far as i know, BMW changed this in the TU (N52KP) which mostly solved the extreme oil consumption problem. However, in specific cases - combination of the car being used predominantly in congested city traffic and ridiculously long OCI (in EU the usual interval suggested by the BC is 30000km) the oil return holes on the pistons would get blocked and the oil consumption skyrockets. BMW determined this to be due to unfavorable positioning of the return holes and in April 2010 updated pistons were introduced. I think there were pictures of them side by side with the old pistons in a German forum, google it. However, the cost of replacement is quite high and in my opinion not justified.

Anyway, seems like to get any significant improvement you will have to take out the pistons and replace the rings. Not a simple job, but if you can do it yourself then the cost will be low as the components are pretty cheap.

I'm pretty sure I did install the valve stem seals correctly. I took the spring off, took the old one off, placed the small protecting foil over the valve stem, placed the new seals, pressed them down as hard as I could, installed the springs back. That blue startup smoke you can see in my earlier posts is completely gone now, so I don't think this was completely in vain, but I still burn oil. I have checked pretty thoroughly for leaks, but something that leaks out 2l of oil in 700km should be seen at the first glance, I think.

I plan on tearing down the engine myself and changing the piston rings, but the pistons will have to stay: I already invested a lot more then I would have liked into this car, and can't afford the pistons.

Do you think the job can be done with the engine in place? Do you have any suggestions for flex/dingle ball honing grit or type?
Thanks!

Originally Posted by acmf

Joining the bandwagon with my N52B25 story.

Started and ran fine, but eventually I got tired of oil consumption that got progressively worse and lately increased to 1l per 1500km. Fixing leaks and replacing valve cover didn't address the issue much.

Decided to bite the bullet and have it checked, hoping that replacing pistons and rings with post-2010 fixed versions would be enough.

No luck.

Rings weren't stuck, but the pistons banged the hell out of cylinder walls beyond any possibility to get them fixed to fit the repair set of pistons and rings. Getting the block sleeved now. At 115000 kms.

Sounds harsh. Mine is just over 170k km, I hope I'll get away with just a ring replacement. I did not find any significant score marks on borescope, but we will see the truth when the head comes off.🤞

Originally Posted by ptpending

engine block replacement is not so bad thing because if oil is changed at big interval then intake camshaft rod wear it's beds and start to issue funny noises tooo

I only have service history for the first 80k km of the car, however from what I've seen in the cylinder head, I don't think I'll have an issue with this for now.

[E92_BGDoc]

Originally Posted by n00b0rKa

Do you think the job can be done with the engine in place? Do you have any suggestions for flex/dingle ball honing grit or type?
Thanks!

I am not a mechanic, but pretty sure it is possible. You will likely need a second person to help though - one to push the connecting rod from below and the other to take the piston out from the top. @neilj35 can probably give you better info on that.

[n00b0rKa]

Originally Posted by E92_BGDoc

I am not a mechanic, but pretty sure it is possible. You will likely need a second person to help though - one to push the connecting rod from below and the other to take the piston out from the top. @neilj35 can probably give you better info on that.

I'm looking forward for his answer as well . I tried to gather some information on this but I haven't had luck yet. Will post anything useful as the story goes.

[laszloczipauer]

Originally Posted by n00b0rKa

I'm looking forward for his answer as well . I tried to gather some information on this but I haven't had luck yet. Will post anything useful as the story goes.

Hello Fellow oil suckers,

I have got the same symptoms and the same engine.

https://www.fcpeuro.com/products/bmw...11617531423kt1

Has that been changed yet? I am unsure if this was brought up to your attention earlier?

I was told this could be the faulty component. Not sure thou'

Btw mine consumes similarily a lot however only in traffic jam/heavy traffic. During highway usage it barely sips 1 deciliter per 1000km which is totally tolerable.

Weird!

Best of luck to you!

[n00b0rKa]

Originally Posted by laszloczipauer

Hello Fellow oil suckers,

I have got the same symptoms and the same engine.

https://www.fcpeuro.com/products/bmw...11617531423kt1

Has that been changed yet? I am unsure if this was brought up to your attention earlier?

I was told this could be the faulty component. Not sure thou'

Btw mine consumes similarily a lot however only in traffic jam/heavy traffic. During highway usage it barely sips 1 deciliter per 1000km which is totally tolerable.

Weird!

Best of luck to you!

Hello!
Yes, I've replaced this already. I referred to this as PCV (positive crankcase ventilation system). Thank you for your suggestion!

nbK

[richievn]

Me 2 with the n52b25 oil consumption. It appears the piston ring is the only possible culprit left as I already replaced other parts.

However, given the known issue of the B25 ring design and that I cant find a good B30 where I live, should I proceed with honing the wall to 3.0 and grab a set of used b30 piston, conrod with a new set of bearing to fix the problem permanently while gaining some more horsepower?

[n00b0rKa]

Originally Posted by richievn

Me 2 with the n52b25 oil consumption. It appears the piston ring is the only possible culprit left as I already replaced other parts.

However, given the known issue of the B25 ring design and that I cant find a good B30 where I live, should I proceed with honing the wall to 3.0 and grab a set of used b30 piston, conrod with a new set of bearing to fix the problem permanently while gaining some more horsepower?

As I said on the other thread, I'm no expert, but that route requires a professional shop which works on aluminum blocks - not something to find on every corner where I live. You should also think about who will flash your ECU. I haven't done any research on this so don't take these as facts.

[BuildAndDrive]

I have a BMW e90 325i with the n52b25 engine and tried EVERYTHING to fix the oil consumption issue (change CCV, seafoam cylinders etc) none of it worked and my oil consumption went from around 1L/1000kms to 1L/300kms.

Eventually I found a donor engine that super cheap on ebay (for a reason) and started to rebuild the engine. So if you still have the car and want to rebuild the engine, I am releasing DIY tutorial videos every week on my youtube channel if you want to follow along. It wasn't too difficult with the right tools... it just took a lot of time!

[Scuzone]

Sorry Im So Late here, What Oil are you using? My Simp solution is Pentosin 5w30HP synthetic only. Then throw a Bottle of Lucas synthetic Oil Stabilizer in. This will give you a few more miles between refilling CrankCase. I went from burning a qt every 300 miles at 122k to about a quart every 3500 miles now with 195K and a annual Oil Change. Only using Hengst Filters as well. I have 2 325xi,s a 328xi and a MiniR50 All on pentosin. And I don't think the disa should be oiled. You may need a intake gasket