Engine oil consumption issues
 

Hello.

So I am lately speaking to few car enthusiasts here in Slovenia and they all tell me that Volvos 2.0 D5 diesels all have weird repeating issues with oil consumption after 50-100 thousand KM (so every 50.000 - 100.000). When I was buying my V90, I never heard any of these mentions or issues but now with mine, I'm actually experiencing it for the second time now.

I bought car with 66.000 driven KM. At approx. 110.000 my car was eating 1L oil per 4000-5000km. I actually got dash warning that I need to add 1L of oil and oil was bellow minimum. I do oil replacements every 10-15K km instead of 30K recommended by dealer. Now at 110.000km my car had replaced head gasket, brushed head, pistons, piston rings, connecting rod bearings and I perhaps something more... Now I have 130.000km and it seems excess oil consumption is back again... Not as much, but its already 6-7 bars down since service. When I bought car 66-110K I had zero to 2 bars oil consumption between service intervals...

I am considering replacing my lovely V90 because of this extremely expensive issue. Any one else having the same? Am I really the lone wolf with these issues?

Hi there!

As far as I know VEA engines D5,D4,D3 and D2 made until 2017 and til some engine series had problems with piston rings ...So Volvo redesigned rings and need to be replaced with pistons also...They say they fix it...But who knows?!

Good luck!

My understanding is that the oil control piston ring was redesigned to make it easier for engine oil to drain from the combustion chamber into the crankcase.

The original oil control ring had very small holes to allow oil through, and these holes were easily blocked. If these holes become blocked then engine oil will remain in the combustion chamber and will be burnt along with the fuel and air. This will increase oil consumption.

The new design of oil control ring has much larger holes that are more difficult to block. The new ring is also different in construction and can't be fitted to earlier pistons. This means that the piston also has to be replaced.

My understanding is that the new ring design was introduced in 2015, and I suspect that all SPA-platformed Volvos (V60, V90, S60, S90, XC-everything) will therefore have the new design of piston and ring.

The fact that you are reporting oil consumption issues for a V90 suggests that the new design of oil control ring doesn't, however, address the root cause of the oil consumption issue.

I am trying to establish the root cause of high oil consumption in VEA engines, and this is proving difficult to achieve.

https://www.volvoforums.org.uk/showthread.php?t=316027

I imagine that Volvo knows the answer, but I imagine that they won't be sharing that answer any time soon.

Do you know what the condition of the pistons and valves was when your engine was repaired? Was there any carbon build-up? If so, where was this? On the valves? On the pistons? If on the pistons, then where on the pistons? Around the edges? On the top?

Sorry for all of these questions. :(

Oil control rings, the lower of the ring set, are not there to let oil drain from the combustion chamber to the sump. They are oil scraper rings that are meant to prevent oil from the under piston area from entering the combustion chamber in the first place. Any oil that gets into the chamber from a closed breathing system should be burnt in the power stroke of the cylinder and ditto any excess fuel injected late during a DPF regeneration cycle, assuming Volvo uses that technique.
Any oil or fuel that leaks down from the cylinder to the sump through any large gap [there's always a gap in every ring on every piston] is basically contaminating the lubricating oil.

So I believe that while the piston ring modification described in the post above may be correct, I doubt very much that the principle described for the need for modified oil scraper rings is correct.

Apologies for any inaccuracies in my description. I'm not a car mechanic.

The Volvo Guy is better than me at explaining the problem that earlier VEA engines have.

https://www.youtube.com/watch?v=8yJoHgwiwio

He says that the new-style ring was introduced in 2016 but I'm not certain that he is correct.

That, however, is a minor detail. The important things that I see are that: -

1) There is carbon build-up in the engine.

2) This carbon blocks the very small holes in the oil control rings, and causes engine oil to remain in the combustion chamber instead of being returned to the sump.

My concern is that, perhaps, the new design of oil control ring simply means that it will take a bit longer for the (larger) holes to get blocked.

I note that jackysi's V90 is the first instance that I am aware of wherein a SPA-based vehicle is showing high oil consumption, but perhaps this is because very few of these vehicles have achieved the mileage required to exhibit the problem.

I wonder how that would stand up to a good will request for an early car out of warranty and requiring the work done since Volvo are aware of the issue.

Basically that clarification is the opposite of the original post and the symptoms are probably high oil consumption due to oil being burnt in the cylinders due to it not being scraped off the cylinder walls. This far more possible.

I’m sorry if it sounded pedantic but its important that mistaken information is not propagated and possibly repeated.

Please correct me if I am wrong, but if there are oil control rings, then the oil is always going to be scraped off the cylinder walls.

The only thing that would prevent oil scraping is extreme wear of the piston rings or cylinders.

The question is about what happens to the oil after it has been scraped. Does it stay in the combustion chamber, or does it get returned to the sump via the holes in the oil control rings?

I am guessing that the VEA engine will always create a small amount of carbon, and if the holes in the oil control rings are too small, then that carbon will slowly start to block those holes.

I am also guessing that any scraped oil that is left in the combustion chamber will cause an increase in the production of carbon because the engine oil remaining in the combustion chamber will adversely affect the stoichiometry of the fuel/air mix.

I am guessing that this increased carbon will block more holes until they're all blocked and that this, in turn, will eventually create a serious problem regarding the build-up of carbon.

Am I extending my hypothesis too far?

I think, that all the stories about the high oil consumption and malfunctioning EGR valves with blocked coolers are well related. Even a tiny amount of oil in the mixture would produce soot.

Would tiny amounts of engine oil getting into the combustion chamber of a diesel engine create significantly more soot?