Oil & filter change - cold or warm engine?

[Babylon]

I once attended an engine service where the engineer preferred to drain the old oil cold, rather than warm the engine for ten minutes first. He did this because he said it reduced the amount of oil spilt into the bilges when changing the filter. He then measured the new oil level on the dipstick cold.

Is this bilge or does it make any sense?

 

[rafiki_]

No question, if the engine can run, run it for 20 mins. You are most unlikely to rid the sump of cold oil. In any case, if you use a Vac pump thru the dipstick, as most folk do, then unless your cold oil is full of fuel, it will be too thick to pull up the vac hose.

At your lesson, your "engineer" definitely was not an engineer, but a half a job merchant.

 

[aluijten]

I understand the logic but I do no agree. The point of changing the oil is to get as much as possible of the old and saturated oil out and not to minimize the oil spill in the bilge. There are other ways to prevent that.

 

[David52]

I'm sure it depends where the filter is located on the engine and within the compartment. But I always manage to reduce the amount of oil in the bilge by putting an open container under it! And always change the oil warm.

Good luck,

GreyishBeard

 

[vyv_cox]

Oil separates out when it goes cold. Solids, water, sludge need to be incorporated into a homogeneous hot mixture to ensure as many contaminants as possible come out with the old oil. As already said, cold oil barely squeezes out through a vacuum pump anyway, it would take a very long time to extract it.

I don't remember ever hearing this dubious advice before.

 

[Nostrodamus]

Should you check your oil on the dipstick when it is hot or cold and how much difference would it make between hot and cold. I was always aught on a car I should do it whilst the engine is still warm.

 

[Novachris]

Should you check your oil on the dipstick when it is hot or cold and how much difference would it make between hot and cold. I was always aught on a car I should do it whilst the engine is still warm.

You need to wait a while for the oil to drain back into the sump to get a correct reading.

 

[alant]

I once attended an engine service where the engineer preferred to drain the old oil cold, rather than warm the engine for ten minutes first. He did this because he said it reduced the amount of oil spilt into the bilges when changing the filter. He then measured the new oil level on the dipstick cold.

Is this bilge or does it make any sense?

Just had my diesel car oil/filter changed.

1st question when I delivered it, was how warm the engine was.

Cold oil will be thicker & not run out, leaving crud behind with the old.

 

[David52]

Oil level on the Dioscuri should be done cold, or after a period of rest. When the engine is running the oil is distributed around the engine and will take some time to run back into the sump once the engine is stopped and will "under read" if no allowed to settle. With some automatic gearboxes (automotive) oil level needs to be measured at operating temperature to ensure room for expansion etc, however the level of lubricant oil is not so critical.

 

[vyv_cox]

Sorry, no idea what a Dioscuri is, but unless it's an enormous engine how much are we talking about? 100 ml maximum held in most small engines for 30 seconds? Most dipsticks wouldn't see it.

 

[bluedragon]

I changed the oil in our 2020 cold a few weeks back because it was down due to a new fuel filter unit being fitted so couldn't start the engine. No probs at all getting all the old oil out via vacuum pump, and even since then the new oil has barely discoloured, so sludge etc left behind wasn't an issue. But I should say it's a fairly new engine (500 hrs) and the oil wasn't really that dirty. Might be more of an issue on older engines.

 

[prv]

Sorry, no idea what a Dioscuri is

I suspect it's an erroneous smartphone correction from "dipstick"

See eg http://damnyouautocorrect.com/

Pete

 

[rob2]

I've never managed to avoid a few splashes of oil during a change - and I favour warm oil. Just getting the filter off the side of the engine (Mitsubishi) always dribbles a bit and sometimes the tub that was to catch the spills falls over. One way to think of it is that in spilling the oil, you get to thoroughly clean the bilges, draining the water tank as you do so. That also ticks off the flushing of the water system in your maintenance schedule!

Rob.

 

[David52]

Yes to dipstick (oops, unsmart phone) and OK - maybe cold check isn't needed, although cold is what we were taught in automotiveland.

 

[The engineer]

My mode of operation is hot removal of the oil and leave the filter removal for a few hours to allow it to drain and reduce mess when removing it if it is a horizontal filter. one last vac and done. This assumes the luxury of time!

 

[alan_d]

Sorry, no idea what a Dioscuri is, but unless it's an enormous engine how much are we talking about? 100 ml maximum held in most small engines for 30 seconds? Most dipsticks wouldn't see it.

I suspect it's an erroneous smartphone correction from "dipstick"

See eg http://damnyouautocorrect.com/

Pete

The Dioscuri are Castor and Pollux, the heavenly twins.

That's not a smart phone, its a pretentious phone.

 

[Blue5]

My mode of operation is hot removal of the oil and leave the filter removal for a few hours to allow it to drain and reduce mess when removing it if it is a horizontal filter. one last vac and done. This assumes the luxury of time!

Agreed, with a plastic bag and plenty of rag for the horizontal filter. For the OP, Volvo operators manual confirms running the engine to operating temperature to make oil removal easier.

As an aside I would like to nominate the inventor of the horizontal oil filter for a Darwin award, sure he had good reason but it defies me, no matter how careful you are some always gets away.

 

[reeac]

My view has always been that the oil should either be really hot or else cold. If the former then it will drain freely, if the latter then at least it will all have drained down into the sump. Fully hot is best. The situation to avoid is that when the engine has been run for a minute or two before draining - no reson to do that in a boat but probably happens with cars at garages if the car is parked for half a day and then driven onto a hoist for servicing.

 

[Rigger Mortice]

Should you check your oil on the dipstick when it is hot or cold and how much difference would it make between hot and cold. I was always aught on a car I should do it whilst the engine is still warm.

AFAIK it makes no difference; you'll get the same reading whatever you do.
If the engine is warm you need to leave it for a short while to let the oil drain into the sump.
If the engine is cold, but you have started it for just a minute or so, you'll have to wait sometime for the oil to drain.
If the engine is cold and hasn't been started you may as well take the reading straightaway. The dipstick will be clean so there's no need even to wipe it. Just take it out, read it and put it back in.

 

[eagleswing]

when you are draining off the old hot oil, measurehow muchyou get out then you will know how much new oil to add. i made a big mistake on my 1st oil change, blithely added 5 quarts when that was too much. i guess about a litre remained in the sump so i was over-full with oil.. bad for the engine to run over the fill line of the dipstick.

and while you are at. it do the gearbox oil also....