OK so my car is burning a good amount of engine oil i've learned to live with it so far and keep adding about a litre every 3000KM approximately,

i switched the car to synthetic as soon as i bought it,

here is my dilemma, the oil gets dark very quick, at about 3000KM its very dark brown, almost black, now that tells me its full of sludge, and the synthetic is cleaning it out. this car takes 6.9 litres of oil and the oil changes are not cheap (coupled with the fact that im buying a jug oh oil between oil changes)...last time i changes oil i used up one full jug between oil changes and it took me about 7500 - 8000 KM between changes and the oil was black by that time

so my question is this, what kind of OCI (oil change interval) should i keep doing ? i dont want to have oil in there that's not effective anymore, so 5000 KM sounds like a good OCI, but at the same time its very expensive so id like to get the best bang for my dollar ...

 

Well, to give you an idea from my accord.. I took off the head about a year and a half ago and found a fairly high amount of sludge..
I had assumed that the synthetic oil I was using before was turning dark quickly because it was cleaning said sludge, but it wasnt really.. the problem was that the PCV system needed servicing, it was blocked up so moisture was being trapped in the oil, leading to increased sludging..

Basically after changing the pcv valve etc, my first 2 changes oil syn went dark fairly early but its been improving steadily..

So, to the s80, the PCV system is MUCH more complicated on these cars, but you may want to look at that as being one of the main causes of your oil darkening to quickly (in addition to cleaning out whatever oil sludge was already present)..
In the end the only way to tell is by taking a look at the head but this isnt usually an option..

What synthetic you using if you don't mind me asking? I hear that Pennzoil Platinum has a pretty strong detergent pack, so you might do well to use that if you aim is to clear sludge... But yes, definitely make sure your PCV system is in order and stick with the 5000km changes for now...

 

at the OCI i get Castrol Syntec, but when i add oil its always Pennzoil Platinum..i hear the same about PP on every site i go to and its always on sale at walmart here

there is no way to service the PCV except getting to that stupid breather box. as far as i know its not easy, is there some other way i dont know of yet ?

 

Im not sure if we spoke about this before andre, but you are wasting your time judging your OCI by looking at the oil. Honestly, you might as well handle nuclear waste with an oven mit. Dark oil does not mean sludge at all, if anything its probably waste combustion gasses slipping past the rings.

If you are serious about verifying your OCI you need to take an oil sample, send it here:- http://www.blackstone-labs.com/ (or equiv in your area). In the meantime a treatment of AutoRX might help, chances are the rings are a little gummed up and allowing too much blowby. AutoRX can help with this, and sludge. You will need to go back to a basic mineral-based oil if you decide to do an AutoRX treatment. You can switch back when you are done of course.

As pointed out by others a PCV service might help too. I wouldnt describe the system as complicated though, its basically a plastic tank on the block with a couple of pipes coming from it. Clean the tank out, clean the pipes out, replace the ORing seal and you are done.

Might be worth inspecting the turbo plumbing for excessive oil, most likely if there is no sign of a leak, the consumption you are seeing is from the turbos or valve guides. Of course hard driving consumes oil too . How much is a jug of oil by the way? 4l? 5l? Is it visibly burning oil or are you just noticing consumption?

 

I had a car in the past that went 5000 KM with dyno oil coming out dark brown, not black.

Whats the point of an OCI sample check if im adding 1 to 1.5 litres about every 3000 KM or less. All i am noticing is the oil dissapearing off the dip stick, there are no leaks and no oil smell, and no blue smoke, no smoke of any kind.

The PCV is just located in such a darn spot that i dont think im skilled enough to get to, taking off the upper intake manifold and what not is not my cup of tea. i changed the spark plugs and small things like that in the past but never pulled the manifold off...

the jugs i buy are 4.4 Litres, and ive been using synthetic since i got the car

i am leaning towards the clogged pcv/ oil trap, sometimes during this last winter on cold mornings the engine would stumble and throw a check engine light, i would reset it, and it would not come back unless the engine stumbled again, this also may happen if she sat for a few days without being on,, i think the oil gums up in that box and doesnt pass through...

the synthetic is taking the sludge out slowly and thats why its getting dark so fast, also the engine may be running rich because the excess gasses are not being burn through the PCV and thus contaminating the oil, dunno with what i guess with carbon ? maybe just burning the oil due to higher temperature in the combustion chamber because hot gasses are not able to escape....

i duno why this car needed a box, didnt they realize it would obviously get clogged ? why couldnt they just use a simple pcv valve and make it part of maintenance, its like a five dollar part on all other cars, everything is so over engendered on these stupid cars

 

The main reason is to find out exactly what is in the oil causing it to darken. All depends on weather you care to know or not of course. It's like a blood test, they can tell all kinds of interesting things from it. They can still calculate the correct values as long as you know how much oil was added.

Im adding about 1lt/500 miles right now with the same symptoms, no burning, minimal oil deposits in the turbo plumbing. I'm pretty sure most of it is getting out the PCV. When I first got the car it was leaking 1qt/30 miles out the PCV, I kid you not! The hose clamp at the bottom of the PCV was loose, tightend it and there has been an improvement, but im pretty sure the oring is leaking too. Thats on my todo list.

 

well we both dont see any leaks on the floor? where is it leaking to ?

i found some good instructions and a few S70 guides with pictures, but this still seems hard, and there is no oil trap kit anywhere, so i wount really know what i need until i woul get in there, ansd i cant afford the downtime,

Volvo dealer is asking $400-500 parts and labour included plus tax canadian to clear the pcv system and replace the stupid box i might do that later in the year when i can afford it a bit easier than now...also if synthetic is slowly cleaning it out, what if i just dont do anything will it clean out the pcv system and the box ?

 

I think in my case its leaking onto the tray underneath the motor. If I park the car on a gradiant it will drip oil, level ground not so much.

Ive read that that might work, but really if you want to use the oil method to clean it, move to a mineral oil with minimal additives and use AutoRX, or use on oil that contains a significant amount of detergents, turbo diesel oils generally fit the mark.

I've use the former method with other turbo cars with success. In your case, I guess since you are consuming so much oil it might be worth going the detergent oil route. That has also worked for me on turbo cars too. An oil of correct viscosity designated as "HD" will do. How often you want to change the oil and filter during this is up to you. I think I'd go with a new filter every 500 miles and maybe a half drain/fill. YMMV

 

i will probably do just that, i took a flash light today and found the box, it all looks dry down there except for one stain, and then it hit me, every time i get an oil change i see a few drop of oil for a few days then it dissapears


i mean its like they overfill the oil it leaks out of the box and then it doesnt leak anymore... is that even possible ?

i mean the manual says my engine takes 6.9 Litres of oil, and that a lot, i know its got two turbos, but a regular nissan 3.0L V6 takes only 4L of oil

 

Cant compare volvo to Nissan man, this is a special breed of car the is over engineered with a ridiculously large oil pan.... Its odd yes, but I guess its extra protection

But if you want to do cleaning out using synth, Pennzoil Platinum is the way.. but its also worth looking into AutoRX with some dino oil

 

IPD now sells a PVC parts kit for S80s

 

whats the link, i never bought anything from there, always used canadian sites

im just going to do what i have always been doing with this car probably anyways

 

I have heard that adding one qt. of ATF at every oil change will clean up a gunky engine. I mistakenly added 3 quarts of ATF when doing an oil change on my 96 850 Turbo. This was over a year ago and it cleaned it up and quieted it down. BTW it has 260K on it and running as strong as ever and it looses about 1/2 qt. between changes. I used only standard 10-30 (whatever was on sale) changed at 5K.