diesel engine oil goes black very quickly, that is normal due to the car being an "oil burner", it does not however mean your oil has lost any of its viscosity and to do another oil change would quite frankly, be a waste of your money as it would go black again very quickly.

Realistically, how quickly? When I have done previous oil changes on diesels granted the change was quick. However this time it was black straight after the change.

not straight after the change, within a couple of days (depending on mileage covered) sounds like your garage did not completely empty the sump.

Exactly - that was my view also, hence the reason I am considering getting it done again. I guess the only real way to know it's been done properly is to to it yourself unless the garage can guarantee they drain it via the sump.

Am not sure what Volvo dealers do.

Kastner in Exeter did mine on Monday and I assume they did it properly as I was charged for a new sump washer. In honesty I wouldn't worry about it as you are looking at a small amount of contamination.

I guess you get that with a sump drain also - I doubt either method gets it all out.

To put my mind at rest I will call the dealer in the morning and ask how they do it.

Would actually be good to do an experiment with one of them then remove the sump plug and wee how much comes out - that would be the conclusive test for me.

I've just changed my oil so decided to buy one of the pumps to test.

I went for the electric one, but from Amazon instead of Ebay as it was half the price!

All went very well, took a little longer than expected to pump the oil out, but it did it with no problems.

On refilling I put in 5.1Litres which has put it about 9/10 of the way up the normal range on the dipstick.

So Going on the fact that it holds 5.5 Litres Max, I'd reckon there is about 300-400ml of oil in - so about a coke can of oil.

I've never done a sump plug drain on this car, but on all other cars I've done I've never managed to get the full amount of new oil in after and would hazard a guess at it being similar.