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Why isn’t my oil black?


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The short question is just that. My oil is a beautiful pale brown even after a 150 mile reasonably high speed drive. This has never happened before.


When I do an oil change on my 300TDi the new oil turns back very quickly. It’s helpful, as it can be readily seen on the dipstick and I recheck the level a few times quite soon after the job is done.

I did a change of oil and filter a few days ago. I don’t have my file with me but the interval will have been roughly 5-6K miles. This time I replaced both oil cooler pipes (originals on there) and was extra careful with quantities, eventually filling with 6litres plus what I needed to fill the filter before I fitted that.

I was just a little puzzled before we left today on a camping trip as when I checked I could hardly see the level.

Due to the oil cooler pipe change, I was slightly worried about leaks on the new pipe unions but it was pouring with rain for the 3 hour journey so didn’t stop to check until my paranoid self said that the oil pressure was a tad lower than normal. There were no leaks. 

When I checked, the stuff is still almost translucent and thin and very hard to see, especially at the side of the road. Could it have been my pipe change and my old pipes coloured it quickly  Diesel oils go black quickly anyway don’t they?

it’s now dark and I will look again in the morning  but in the meantime, what do you think?

 

 

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Well I had a look and it is slowly turning darker but only slightly. I might be wrong but I’m sure bits fine dark almost immediately. The rad has been off once in my time but I didn’t  intentionally drain the oil cooler at that time. Maybe it’s the new hoses that are keeping it clean. 🤷🏻‍♂️

I also managed to overfill it when I couldn’t see the level at the side of the road. There’s about 1 litre excess in there. Not sure whether to attempt to drain it a little if I find a suitable container on a campsite. We are only doing an occasional few miles over the next couple of weeks, most days not moving. Then a straight 150 miles home. 

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On 9/24/2022 at 10:25 AM, Snagger said:

The new filter is solid and you have zero flow, so all the many stuff is still in the galleries and the new oil undisturbed in the sump… 😜

That's almost what I was thinking...except my version of doom and destruction had an unprimed oil pump...

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After I did the engine re-build - it took a good bit of time for the oil to go dark - i.e. from an oil change its the dirty oil left over that does the initial "darkening" in my opinion, if you did the oil cooler pipes than thats a good bit further old oil removed from the system, I would'nt be worry.

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Depends on the oil, fequency of changes etc

My oil takes 2k to get to dark, but still translucent. If it was Shell Rimula then add another 2k to that.  But I clean my engines, inside and out, when I first buy a vehicle. Drop the sump, clean the pickup, use Comma engine flush, clean the oil cooler. It's because I am very anal.  Hell I even replace the oil seprator at factory mileage

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I dropped into a little garage today and was waved over the pit before the guy started on the morning’s job (a standard service on a local car). That was so nice of him.

Together we dropped about a litre from the sump to get it down to ‘max’. It’s quite hard with a magnetic sump plug and I did warn him that it prefers to attach to the side of the drain hole.

Anyway I was happy to get the level down and it was marginally easier to see it, as it is now slightly more coloured after a few more miles, than it was last Thursday, in the rain and dull evening.

It must be the oil cooler pipes and maybe I’m a little early with the change (based on miles)

I’ll be watching the pressure on the trip home later this week. Short hops on Anglesey aren’t getting it up to oil temp and the pressure is staying above 2Bar. I have no reason to think of a low pressure issue, except a few minutes where it seemed to be lower than the normal low. The bore honing, re-ringing and a new piston, was all done 10K miles ago in Jan 2020 at 125K miles (on this engine, a Turner build when the vehicle was at 39K miles). The big end shells at that time showed very little wear. 

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On 9/26/2022 at 11:50 PM, Snagger said:

Magnetic plugs on the sump would be a nuisance, though they are good for transmissions and axles.  I favour FilterMags - they do the same thing but trap all the particles in the lump you toss out.

I've got some flat super strong magnets I attach to the oil filter, when the filter comes off I swap the magnets over to the next filter. - I'm sure I saw someone else on here doing it.

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On 9/26/2022 at 11:50 PM, Snagger said:

 I favour FilterMags - they do the same thing but trap all the particles in the lump you toss out.

 

16 minutes ago, Maverik said:

I attach to the oil filter, when the filter comes off I swap the magnets over to the next filter.

Interesting. I don’t know the oil path through the filter but isn’t there a chance that the particles are held in an undesirable part of the flow?

The sump plug isn’t normally a problem except for a few seconds this week doing that partial drain. 

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Some cars have factory magnetic sump plugs, never been a bother for me.

Filter flow is, I understand, in through the outside holes and out the centre.

I don't think there's any harm having a magnet on the filter, two benefits, I suppose, are you may stop the filter clogging so quickly, and you may stop particles from being sent through when the filter is in bypass mode, with thick oil and a cold start.

My feeling is they would need to be very, very strong to pick particles up while the engine is running, and your probably better putting them on the sump so they get caught while the oil is essentially stationary.

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FilterMag uses very strong magnets.  Anything caught by them was already inside the filter housing, but gets trapped before the filer element and is never going to escape.  I was very surprised how much it caught on a well run in, well serviced engine at the next 5000 mile service.

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6 hours ago, Peaklander said:

Interesting. I don’t know the oil path through the filter but isn’t there a chance that the particles are held in an undesirable part of the flow?

From the oil pump to the outside of the filter into the middle then off to lub the engine, hence sticking some magnets onto the housing is a perfect place for picking up any heavy magnetic bits and keeping them in a safe place.

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Don’t underestimate the benefits of convenience of location.  A strong magnet on the sump will hold the ferritic particles in position, but will do nothing to help remove them on the next oil change (if left in place, it will completely inhibit their flushing).  A magnetic drain plug will help remove much of it, but some may get brushed off inside the sump during removal if the collection is large.  That will likely get washed away by the drain flow, but you then have to scrupulously clean the plug despite it clinging to the particles in order for it to seal well on refitting.  A filter mag stays on while removing the filter and is then transferred, so all those particles are tapped and removed from the engine without mess, cross contamination or impediment to a good seal.  In a nutshell, they are the most effective method of ferritic particle removal not just because the magnet is one of the strongest and largest you could fit, but also because of the siting and cleanliness of removal and refitting.

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