Root cause of high oil consumption in VEA diesel engines?

[Sotosound]

As per the following thread, there appears to have been a problem with the design of the piston oil control ring on earlier VEA diesel engines which, allegedly, can lead to a massive increase in oil consumption.

https://www.volvoforums.org.uk/showthread.php?t=310632


HIGH OIL CONSUMPTION AND CARBON BUILD-UP

The contention is that the drain holes in these oil control rings are too small, and can easily become blocked. Once blocked, they can no longer drain engine oil back from the combustion chamber into the crankcase. This oil gets burned along with diesel oil in the combustion chamber instead, causing oil consumption to increase substantially.

My understanding is that this issue is accompanied by carbon build-up on the pistons. Whether or not the two things are connected by a causal link is, however, less clear.


NEW OIL CONTROL RING DESIGN. HAS IT BEEN USED IN VEA DIESEL ENGINES?

A revised 3-part design of oil control ring that was apparently introduced for petrol engines sometime in 2015 appears to have much larger holes that are less prone to becoming blocked. Whether this change was implemented in diesels is unknown to me. If it was then whether or not it has resolved the issue for newer cars is currently unknown to me.

Are any later Volvo diesel cars developing high oil consumption?


NOW BOTH OF OUR ARE CARS ARE AFFECTED

As some members will know, high oil consumption is already a problem regarding my wife’s 2015 V60 D3 Geartronic, and it’s very likely that blocked drain holes in the oil control rings are the culprit.

Strangely, my own 2014 V70 D4 Geartronic seemed unaffected, however, UNTIL NOW! Now it’s showing an increase in oil consumption.

In late 2020, it required 0.5 litres of oil after 9,000.

Then, a few weeks ago, it required 0.5 litres after 4,500 miles.

This week, it required 0.5 litres after only 1,000 miles.

I suspect that this trend can only get worse.



WHAT IS THE ACTUAL ROOT CAUSE?

A very knowledgeable person has suggested that the oil control rings might not be the true problem, however. So I started to look more carefully at things and tried to keep an open mind while doing so.

The first question that comes to mind is “Why would oil consumption remain very low for 130,000 miles and then suddenly start to increase dramatically?”

Obviously, and assuming that blocked drain holes in the oil control rings are the cause of the high oil consumption, the holes in the old style of oil control ring were clear enough for six years, and successfully allowed oil to drain down into the crankcase for 130,000 miles over those six years. Then either something changed, or an ongoing process reached a critical point wherein it became so bad that the holes got blocked, and engine oil started to get burned in the combustion chamber instead of getting drained back into the crankcase.

My second question has to be “What might cause those drain holes to get blocked, and why would it take so long for them to get blocked?”

Is there a contaminant of some kind that builds up and, if so, what causes the creation of this contaminant?

Is there a carbon build-up, and is this the contaminant that blocks the holes? If so, then why is there a carbon build-up?

It has been suggested that direct injection might be the cause, but all Volvo diesels have been direct injection since the original D5 was introduced, so why would the VEA diesels be any different in this respect?

Is the carbon build-up caused by failing valve stem oil seals allowing enough oil into the cylinder to start the build-up of carbon that eventually causes the drain holes to become blocked, and do the blocked holes simply serve as a multiplier for the carbon build-up?

Are the blocked drain holes simply the long-term consequence of lubrication oil in a diesel always being black and contaminated in combination with those drain holes being too small?



LOOKING AHEAD

I don’t know the answers to the above questions, but my worry is that if the root cause of the high oil consumption isn’t correctly identified and addressed then any repairs will only be temporary.

• A straightforward change of piston rings and valve oil seals might simply reset the clock on the problem, and after 4 or 5 years it’ll be time for another set of rings and seals.

• If the new oil control ring design does enable oil to drain more effectively and for longer, then a change to the new design of piston and oil control rings might not only maintain low oil consumption; it might also allow the actual root cause to go unnoticed for longer, meaning potentially bigger problems later on.

Now, we could sell our V60 D3 and V70 D4 and leave the Volvo brand behind, but we actually like Volvos. We also, however, bought our Volvos in part due to Volvo’s reputation for the longevity of their products. To find out that this reputation is now history, and that our own experiences are sadly actually proving that, is very concerning and upsetting.



ANY VIEWS?

Has anyone on this esteemed forum got any views about this?

Can anyone add to the knowledge or point out corrections?

Most especially, can anyone offer us some hope?