oil check question - brain says cold, handbook says warm

[Scudetto]

guys,

I've always thought that on a petrol car, you check the oil when the engine's off and cold (although when my mate went to collect his new Boxster back in 1997, the Porsche dealer said on that car it should be checked with the engine running - dry sump or something?...I don't remember now).

Anyway, just reading the handbook on my car, and it says "Check engine oil level with the engine at operating temperature". If that's what it says, then that's what I'll do, but I would like to understand if there's a reason why is says to perform this check when warm, rather than cold. Any ideas?

Thank you!

To be fair, I've never noticed much of a difference in the level when I've checked my oil, be it hot or cold.

As a rule, it's easier to check the level on the dipstick when it's cold as it's less likely to just run off.

Try the check hot and cold............let us know if there is any change

[Scudetto]

good thinking, bud! i'll put it to the hot v cold challenge tomorrow

[steveisfrowning]

i suppose it depends on where they mark the dipstick????
Like Sparks said, it's easier to check when cold as it's less runny. I know you know this.

[antpal]

Glad i spotted this thread, as i was about to start something similar!

My oil check is a right pain. Do it cold, it reads full - do it hot, it reads empty - do it warm, it reads full!

Will be interesting to hear Scudettos results!!

[wlm8361]

Never do it hot. Should be done cold. Warm should be only slightly lower than cold level.

[antpal]

......checking my owners manual now....

[antpal]

on a side note, i never knew door pockets etc were called 'Oddment Recesses'

I've never found hot or cold to make a significant difference to be honest.

[symon]

Cold, simply because it is easier to get an accurate reading.

[Scudetto]

Originally Posted by symon

Cold, simply because it is easier to get an accurate reading.

...which is what i have been taught, and it seems logical to me...but there must be a reason why MB begs to differ on this matter...it's not a stupid company after all, so that's why i want to get to the bottom of why it says 'warm', when we say 'cold'.

[Gibbo]

If you check it when it's cold, remember to put a jumper on

[antpal]

I'm no mechanic, but i can't see the logic in warm or hot. And I see even less logic in 'a few minutes after the engine has been switched off', as surely by this point there would be a fair amount of oil dispersed around the engine and its components.
Right???

[steveisfrowning]

Originally Posted by antpal

I'm no mechanic, but i can't see the logic in warm or hot. And I see even less logic in 'a few minutes after the engine has been switched off', as surely by this point there would be a fair amount of oil dispersed around the engine and its components.
Right???

which was my point about, depends where the mark is on the dipstick

if it's cold, it's all in the sump, so easy to read in terms of

a) it's all there
b) viscosity (gooey)

If it's warm surely there is a double whammy of

a) it's not all there
b) viscosity (thin)

I suppose I was wondering if MB could make allowances for a) - but surely that would depend on how clear the pipes were and the efficiency of the pump?

Doesn't make sense, I tells ee.

[antpal]

The worst thing i've found about checking cold, is that when i remove the dipstick, it drags oil up the dipstick pipe. So, when i re-insert and pull out to do the actual check the whole dipstick is usually covered!!

[SENNA1]

I cannot see the difference on my cars

[antpal]

Probably because your engines are always warm

[Al Faromeo]

Dry sump: running temp; - because there won't be a lot to check when the car's not been running as most of the oil will be in the sump ...
Wet sump (i.e. Other): cold.

[MalcQV]

Looking at Wiki I can't workout if road going 190E's are all wet sump.
It is imperative a dry sump engine is measured when running (as Al says above).

[antpal]

Its a mystery!
To pull away from the MB issue slightly, i just followed AR's advice (pictured), and got an accurate reading first time (which is a rarity!)

[kickstart68]

Hi

Expect with the hot / cold thing, either is fine as long as sufficient time is allowed for oil to run down to the sump. Which won't take long if hot, but might be a bit of an issue if someone starts the engine for a few seconds when cold and then tries to check the oil.

With wet sump engines, suspect it varies between models. Would expect what they want is to pump any oil that has drained to the sump back into the oil tank. Whether after that the marks equate to the engine running or not is another question.

All the best

Keith

[Al Faromeo]

Originally Posted by kickstart68

Hi

Expect with the hot / cold thing, either is fine as long as sufficient time is allowed for oil to run down to the sump.

I believe you are not right, i.e. hot/cold makes a huge difference depending on the engine type.

From Wiki:

Originally Posted by Wiki

In a dry sump, the oil still falls to the base of the engine, but rather than being allowed to collect in a reservoir style oil sump it falls into a much shallower sump where it is removed by one or more externally mounted scavenge pumps and is pumped into an external reservoir where it is both cooled and deaerated.

When the engine is cold, most if not all of the oil will be in the extrenal reservoir so there will not be a whole lot to check.

[Joss]

Originally Posted by Mymatemarmite

To be fair, I've never noticed much of a difference in the level when I've checked my oil, be it hot or cold.

As a rule, it's easier to check the level on the dipstick when it's cold as it's less likely to just run off.

Try the check hot and cold............let us know if there is any change

Really. All alfa's I dip seem to vary loads when hot. The GTA especially gets half a max to min distance again when hot. All my ts's went up a fair bit too and the diseasel

Originally Posted by Joss

Really. All alfa's I dip seem to vary loads when hot. The GTA especially gets half a max to min distance again when hot. All my ts's went up a fair bit too and the diseasel

I've never seen that kind of difference on mine mate, but then again, Alfas, especially GTAs, are a law unto themselves anyway

Of course there is also the difference between hot, and hot.

When checking mine it's either cold, or has covered just a couple of miles to the workshop at work. Enough to bring the second bar onto the oil temp gauge, but not as hot as it would be after a spirited drive.

[Joss]

Ah se mine varies from cold to raped all the way to Autolusso