Oil still black after change and vacuum oil extractors

[visor_down]

Hi all

Quick query that I have been unable to find a clear answer to on searching here and elsewhere on www.

Did oil change on petrol car (68k), warmed up before draining and left to drain for at least half hour. Went for a run after initial fill and on topping it up it was accidentally overfilled so excess as extracted out of the dipstick tube, the thing is the extracted stuff (around 400ml) was black like the oil that had just been drained out?

I understand this could be because the vacuum hose is getting it right out the bottom of the sump, but i would have thought the run round the block after initial fill would have stirred it up a bit, the oil on the dipstick is clear as you would expect on a new fill.

Just interested on thoughts as to why the extracted stuff was so black and not mixed with the new fill, also surprised it hadn't drained considering the long drain time? Could a sediment of 400-500ml stay in the sump?

cheers

 

[the snooper]

I think you have answered your own question probably some in the sump that didn't quite drain and you hit it with the tube

 

[visor_down]

yes that was my thoughts but curious as to why it wouldn't have mixed with the new fill, not vital just idle curiosity!

 

[the snooper]

the new oil wouldn't have gushed down into the sump so would imagine some did mix then just sat on top, not to mention that the first new oil to enter the engine would be picking up some old oil on the way down

 

[AndyStobbs]

Depends I think on how old the oil drained was. If service work has been neglected oil ends up like black paint. It takes multiple flushes to get it cleanish again. The new oil has mixed without a doubt, but basic art school says its easier to mix dark colours into light ones. It doesn't take a lot of blavk pigment to turn the new oil black.

 

[DrNik]

You never get it all out with a vacuum extractor, also some is held in the oil ways and on webs and in the head, don't worry too much

 

[pedrobedro]

Drain it again and refill it and it will be black again within half an hour, that's what happens in engines running on hydrocarbon fuel. If you don't want the oil to go black convert it to LPG we used to have fork trucks running on it and the oil looked perfect even though the service interval was up. Just because the oil looks clean doesn't mean it is good though as it wears out like any other part, the long chain molecules break down and it gives less protection than your fresh black stuff.

 

[penfold]

I'd be concerned the sump has a layer of sludge in it; the previous owner may have been stretching the service interval.

 

[DAPPH]

You never get it all out with a vacuum extractor, also some is held in the oil ways and on webs and in the head, don't worry too much

There is of course almost 1/2 a litre also hanging around in the oil pump & galleries plus the stuff on the walls. Plus some in the oil filter ..
You didn't change the filter did you ??

If it is that bad, perhaps look at shoving a can of flushing mix in the engine and doing exactly as the instructions say. Then once it's drained down fill with the CORRECT amount of new oil .

 

[brightspark]

dont ever use flushing aditives why loosen the solid crap then flush it through your white metal bearings and then contaminate them garrage asked me if i wanted it doin on guarantee service . no chance i dont want my engine wrecking . if the crap dont move leave well alone

 

[DAPPH]

I've never thought of it that way ., I've never had any probs on an engine , usually diesel ones that I've done it too ...perhaps I've been lucky that the old & new oil filters have taken things out before any pick up took place..

 

[PhillipM]

If the detergent pack in the old oil was saturated, fresh oil with fresh detergents will pull out all the sediment and ****e and turn black very quickly indeed.

More regular oil changes or if you want to clear most of it, do a couple of changes in short order and it should pull most of the crap out.

 

[norlander]

As stated by someone -was the filter changed as well.

+1 on more frequent oil changes to get the oil system cleaned up .

 

[visor_down]

Yes filter was done, has been done with the oil every year (around 10k pa) since new.

 

[Rig Pig]

If your concerned send a sample of the old oil away for analysis, but it's quite normal for engine oil to go black, as the other posts say there is a lot of old oil & carbon left behind after an oil change especially if you use a pump, the heavy particals tend to drop out and lay in the bottom of the sump in the bit that gets left behind!

 

[Robotstar5]

I tend to change my oil every 6 months as although I only do a low annual mileage, a majority of it is short journeys commuting.

 

[Jan]

dont ever use flushing aditives why loosen the solid crap then flush it through your white metal bearings and then contaminate them garrage asked me if i wanted it doin on guarantee service . no chance i dont want my engine wrecking . if the crap dont move leave well alone

Come on: Cast in situ and machined white metal bearings haven't been used since before WWII! Modern shell bearings are much tougher than that.

On a newly acquired used car I always flush it through at least once, if not twice, to get out all the crap before refilling it with fresh oil and putting on a new filter. My latest acquisition - a British built (Rootes) Dodge 50 motor home - had oil in it that was a black as a lump of anthracite in a cellar at midnight with the lights off. Before the flush there was excessive blow by and a significant jet of fumes from the sump breather pipe. After the flush the oil has stayed nice and clean and the blow by has reduced to almost nothing. The previous car (since stolen) was in even worse condition as the person I bought it off had done nothing but put DERV in it during the 5 years he owned it! A double flush later and the oil stayed clean right up to the next oil change and even running on a mix of filtered veg/used sump oil/unleaded it passed the emissions part of the MOT with flying colours. In most cases it's just a matter of making the flushing oil from a 5:2 mix of cheap oil/DERV, only using half the full sump quantity and then only letting the car idle for 2-3 minutes so that it gets into all the little oilways. With 7 litres you have enough to do it twice the first time or just the once and again at the next oil change Despite the number of cars I've done this on over the decades I've never experienced any problems with it.

 

[PhillipM]

I used to run half ATF if I really needed to flush an engine for whatever reason, plenty of detergents in it.

 

[brightspark]

Come on: Cast in situ and machined white metal bearings haven't been used since before WWII! Modern shell bearings are much tougher than that.

white metal bearings is a figure of speech i know there shell bearings,crap is crap and i wouldnt want floating round my engine loose. modern engine oil has detergent and good scouring properties added . theres a firms in america peddling engine flushing and push it on to punters as its a good earner . it was well investigated by trading standards as some punters had wrecked engines that were still under manafacturers warranty and were void by doing so if u think its a good idea to have done all well and good i personaly dont and wouldnt .both sides of the coin have been shown so people can form there own opinion[/http://www.pistonheads.com/gassing/topic.asp?t=1160919

 

[Rig Pig]

Oil company's have massive research budgets but none of the reputable ones produce an engine flush..... The only way to safely remove heavy sludge deposits is to strip down and mechanically clean them out. Modern (quality) oils have excellent detergents in them, if they are changed at the recommended intervals or as required by condition monitoring there will be very little in the way of sludge.