[martinp]

So I have just done an oil change on an i30 2016 1.8l petrol Model.
The oil in the sump was blackish... no surprise there but the oil coming out of the oil filter casing and residue in the oil filter looked brand new?
I collected both oil sources in a bucket and you could clearly see a stratification in the oil with blackish oil at the bottom of the bucket and clear fresh oil at the top.
Oil light is appears to be operating normally i.e. comes on briefly on starting
Should I be worried that the oil is not circulating properly through the engine, sump and oil filter?

[mickd]

Hi,
Clogged /defective filter  or defective bypass in oil pump.
Bypasd allows oil to flow but not filter

Wait for more knowledgeable as I'm using old school thoughts.

[CraigB]

How long is it usually between oil changes and what oil is being used? mineral oil usually turns black.

Could there be residual dirty oil (sludge) sitting in the bottom of the sump from previous changes if it was never drained properly might be due for a engine oil flush treatment.

[nzenigma]

So
I have just done an oil change on an i30 2016 1.8l petrol Model.
The oil in the sump was blackish... no surprise there but the oil coming out of the oil filter casing and residue in the oil filter looked brand new?
I collected both oil sources in a bucket and you could clearly see a stratification in the oil with blackish oil at the bottom of the bucket and clear fresh oil at the top.
Oil light is appears to be operating normally i.e. comes on briefly on starting
Should I be worried that the oil is not circulating properly through the engine, sump and oil filter?

You dont mention K's done between oil change;
or how low the oil was in the collection bucket.
Mick and Craig's Opinions above are all reasonable.
However, mineral oil will allow contaminates to settle to the bottom.
In the good old days they used to filter the top layer and reuse it. It was as clear as when you bought it for half the price of the Mobil product.

[tw2005]

any photos?

[martinp]

Sorry no photos

[martinp]

Thanks for the comment
7,500km between oil changes which have ALL been done by Hyundai service agent until I did this last one.  Therefore I don’t know what oil was used but I will try and find out from service agent. 
I have used a ryco filter with Penrite 5W-30 fully synthetic.
 

[martinp]

How long is it usually between oil changes and what oil is being used? mineral oil usually turns black.

Could there be residual dirty oil (sludge) sitting in the bottom of the sump from previous changes if it was never drained properly might be due for a engine oil flush treatment.

Thanks for the comment
7,500km between oil changes which have ALL been done by Hyundai service agent until I did this last one.  Therefore I don’t know what oil was used but I will try and find out from service agent. 
I have used a ryco filter with Penrite 5W-30 fully synthetic.
I think your point regards possible residue from earlier oil change is a good line of enquiry, but doesn’t all the oil get mixed as it passes through he engine?

[martinp]

Hi,
Clogged /defective filter  or defective bypass in oil pump.
Bypasd allows oil to flow but not filter

Wait for more knowledgeable as I'm using old school thoughts.

Thanks for the comment. Please tell me more about “bypass in oil pump”?  I’m not familiar with this

Cheers
Mule

[nzenigma]

Bi pass has been around since Adam, simply a pressure valve that opens if the filter is clogged.

If a dealer-service department ( instead of a good garage) has been doing your changes, it will probably be done by some cheap lacky ( apprentice) who may or may not have changed the filter and would been using their cheap oil and may have drained the sump properly if he had time.

[mickd]

Bi pass has been around since Adam, simply a pressure valve that opens if the filter is clogged.

If a dealer-service department ( instead of a good garage) has been doing your changes, it will probably be done by some cheap lacky ( apprentice) who may or may not have changed the filter and would been using their cheap oil and may have drained the sump properly if he had time.

@martinp
Spring loaded ball bearing in the oil pump body  that allows oil to flow through engine,  if, it cannot pump oil through the oil filter.
 Ensures that oil flow /pressure is maintained thus preventing engine seizures.
Its a failsafe that has no warning associated with it.