Thread: Hot or cold?

I always change mine soon after a run to operating temp. Theory is that the sediment/sludge will then be in suspension so you will get more gunk out than if you do it cold.

sometimes mine is either warm as i had been running around picking up filter etc...but i do wait for it to cool off to warm so that its no uncomfortable if oil runs down your arm

other times it been cold

Originally Posted by Linds

I always change mine soon after a run to operating temp. Theory is that the sediment/sludge will then be in suspension so you will get more gunk out than if you do it cold.

surely if you don't mix the so called sediment/sludge up by running the engine to running temperature it will be at the bottom of the sump and be expelled when the sump plug is opened? Just a thought.

Hi , I wouldn't go near a hot engine to change the oil , let it cool down give it plenty of time to drain , it should be ok ......

Originally Posted by ted44

surely if you don't mix the so called sediment/sludge up by running the engine to running temperature it will be at the bottom of the sump and be expelled when the sump plug is opened? Just a thought.

Agree and whenever I change any of the oils I always remove the filler plug/cap first.
This greatly increases the drain flow and creates a flushing effect.
And cold is easier and safer than hot.

Cheers,
Paul.

Originally Posted by ted44

surely if you don't mix the so called sediment/sludge up by running the engine to running temperature it will be at the bottom of the sump and be expelled when the sump plug is opened? Just a thought.

The only way to fully drain the sump is to take it off. There would be half litre or so of oily sludge left on the bottom of the sump after the oil has stopped seeping out of the plug hole. I would imagine the more its mixed in after running the engine (i.e. the sooner you change it) the more gunk will come out. I'm sure particulate matter settles overnight as on my last change I fitted a Fumoto drain valve (a tap that opens instead of removing the plug). I went for a 15 - 20 minute drive after the change. I checked the next morning and the oil on the dipstick was very clean and almost invisible, as one would expect immediately after a change, but a little high so I though I would drain a little, easy to do with the tap. The engine was, of course, stone cold. I was shocked that, instead of the honey coloured fresh oil I was expecting, out came a thick black sludge. I had to drain over a litre of sludge before the colour brightened. I was considering draining a litre cold the day after every oil change and topping up a fresh litre. Judging by the oil I got out the next day, it couldn't hurt.

Originally Posted by ugu80

The only way to fully drain the sump is to take it off. There would be half litre or so of oily sludge left on the bottom of the sump after the oil has stopped seeping out of the plug hole. I would imagine the more its mixed in after running the engine (i.e. the sooner you change it) the more gunk will come out. I'm sure particulate matter settles overnight as on my last change I fitted a Fumoto drain valve (a tap that opens instead of removing the plug). I went for a 15 - 20 minute drive after the change. I checked the next morning and the oil on the dipstick was very clean and almost invisible, as one would expect immediately after a change, but a little high so I though I would drain a little, easy to do with the tap. The engine was, of course, stone cold. I was shocked that, instead of the honey coloured fresh oil I was expecting, out came a thick black sludge. I had to drain over a litre of sludge before the colour brightened. I was considering draining a litre cold the day after every oil change and topping up a fresh litre. Judging by the oil I got out the next day, it couldn't hurt.

Thanks for that obviously you would never change oil when red hot. Very interesting about taking the sump off never thought of that, does anyone on here change their oil in this way?

Originally Posted by ugu80

The only way to fully drain the sump is to take it off. There would be half litre or so of oily sludge left on the bottom of the sump after the oil has stopped seeping out of the plug hole.

[snip]

Bingo !

I've actually measured the residual oil left behind in the sump and oil cooler circuit in a Tdi and wile it was quite a few years ago and I can't remember exactly how much it was up around 700+ml, maybe more.

And people wonder why the oil discolours so quickly after an oil change