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Discussion Starter · #1 ·
I changed my oil yesterday using Halfords 5W/40 Fully Synthetic, ran it for 30 miles last night.

I checked the level this morning and it was nigh on black. I thought it took a few hundred miles before it would change??
 

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Dependant on when the oil filter was changed. I would change the filter and oil again while the oil is hot and leave it draining for a good while. This should normaly give that nice clean golden look to the oil on the dipstick when run after filling up with fresh oil. Watch the mits though when you unscrew the drain plug. Could run it for a few miles first to get a bit of value out of the oil, should do no harm.
 

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I concur with Ylee.

I don't want to sound alarmist, but how can fresh oil turn black straight after a change?

Obviously, there is immediate contamination of the fresh oil! But with what?

In my view, this situation must be caused by black sludge, due to a previous owner's lack of regular oil change and use of quality oil.


I would definately take rocker cover off and check area for signs of black sludge.

If this is the cause, then carefull consideration whether to use a engine oil flush (before changing oil again) is required. With some engines, a flush can cause sludge to block internal engine mesh filter (stops pieces of metal getting picked up by oil pump!), resulting in a nackered engine!

The only other cause I can think off, is that the old engine oil is not left long enough to drain properly (or car not standing on flat ground), resulting in old oil still in engine when sump plug replaced.

Hopefully, it's just the latter...
 

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Discussion Starter · #7 ·
The last oil change I had done, I used Mobil 1. This took a couple of hundred miles before it change to the same shade as this Halfords has in 30 miles.

I always change the filter with every oil change.
 

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i drive a '92 c900T with 302k miles on the original engine and turbo and have never had the oil turn black as quickly as yours is, Scottry Mc. in fact, when checking the level immediatelly after a change, the oil looks almost clear on the dipstick, after about 1k miles, i have noted a change in color towards golden, nearing the 2k mile marker and the gold is getting rather dark. 3k mile marker (when i am due for a change) and the oil has never been black, though the gold is fading into a brown by this time usually.

black engine oil would cause me to be alarmed. of course, if the system was not fully drained, then i could understand a quick change in color... and even then, going all the way to black so soon
 

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2.0 LPT 125K miles, oil changed at 120K and the oil is golden, last time I saw oil turn black in that short a time was on an old BSA C15 which was badly in need of a service, that was the last oil change as shortly after the top of the piston came off. Stripped the engine, rebuilt it and included an oil filter inline on the oil return, changed the engine breathing from timed to full flow and it runs with golden oil for its 2k mile oil change and with no oil leaks.
 

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Or alternatively the Halfords oil has a better (different) detergent than previously used oils, and so it's cleaning out and holding in suspension stuff that was left on the innards previously.

My oil stays clean, even though I use a longer service interval than most people on this board. It is often difficult to see on the dipstick for quite a while after it has been changed.

Ther only time I have known oil to go really black quickly has been in diesels.
 

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The only time I've encountered oil going black almost immediately was when I'd done the top end of a friend's 1949 Rolls. I dropped the sump to find out why,and had to use a paint scraper to shift the gunk which was an inch thick. That's where the colour in the oil was coming from, gunk undisturbed for years.
 

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I now that you change the oil for 2 reasons:
1)the oil get oxidation so it loses some lubrican power after a while (hence the 6months-one year limit)
2)to flush away the gunk and the dirt in the engine (hence the x000 miles limit)


So it's important that oil gets dark, otherwise it would leave the gunk in the engine! and the gunk is generated by combusion residuals on the cylinder walls, so it's almost the same for every engine, I don't think that a fresh engine produces less gunk than an old one.
Of course, the dark you see could be gunk deposited in the pan thousends of miles ago. So there's the risk to have the oil saturated with gunk sooner than usual. Which is not bad for the lubricant power of the oil, which is always the same, it's just that the gunk that is produced by the combustion after the oil is saturated is condamned to build up in the pan, as oil can't carry away with it when it's flushed out more gunk than what it has when it's saturated. So it would be advisable to change the oil sooner. (I hope I made myself clear).

So using that oil is like doing an engine flush, but much more gradully, so you don't have to bither about gunk clogging oil passages and all the nasty things an engine flush can do to an "old" engine. A good thing if you ask me.
 

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When I dropped my sump at 173000 miles I was expecting a large amount of goo,but there was none,laquering yes but that was it.
I did however have a devil of a job to drain the oil cooler,the contents were like mollases so I wonder if the cooler does not drain down? If the thermostat is closed I do not see how it can and on start up the contents will not take long to mix with the new oil.
mike
 

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My Aero is due now for a change and, checking the oil this morning, I would say that it is only copper brown after 6000 miles. The trusty steed has 156k miles on it now and has always had "Saab" service so I presume it is Saab oil and filter in the car.
 

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Originally posted by MikeH:
[qb] I did however have a devil of a job to drain the oil cooler,the contents were like mollases so I wonder if the cooler does not drain down? If the thermostat is closed I do not see how it can and on start up the contents will not take long to mix with the new oil.
mike [/qb][/b]
This is why an oil change is best done with the engine warm
 

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Discussion Starter · #17 ·
I getting really confused here chaps.

Some people are saying that the oil turning black instantly is a good sign due to the detergant properties, others are saying that I should stop using fully-synthetic to not attack the seals etc, others saying a flush and others not.
 

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Use whatever oil is recommended in the service manual, if it says use fully synthetic then use it, if not use the recommended mineral oil.

I had a friend with a Renault 19 16V who thought Mobile 1 would be good for it, however, it was too thin at temperature and meant the cylinder head coming off to have repair work done.

I would have thought that most FPT engines require a top grade oil due to the temperatures in the turbo, but I'm not sure about the LPT's

Skiddins
 

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Scotty Mc,

You have the problem that an old engine will have some oil sludge caked onto the sidewalls of the oilways. The risk is that if you don't flush you may not get enough lubrication as the oilways may be blocked. On the other hand flushing will remove the sludge but it may come off in lumps from the bigger oilways and block the smaller ones.

Which you choose depends on the history of your engine and the service it has received. If it has had good oils all its life they will have had detergent in them and there may not be too much deposit in the engine - a flush may clean it. On the other hand an engine that has had a lot of cheap oil and irregular services may be better left undisturbed. It will probably have a shorter life anyway.
 
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