Oil level difference in relation to its temperature

[nidza]

Hello everybody,

 

we had a discussion a while ago which ended full of amusements but without any useful conclusions.

 

To show how significantly oil thickness and volume is affected by its temperature I did a little experiment, outside of my office. 

 

Just upon arrival, after approx. 2 minutes, oil temperature 100 degrees:

 

After approx. 20 minutes, oil temperature 63 degrees, you can see now it's on exact maximum. It is still expanded, but now drained back into the sump.

 

After approx 1 hour, shirking began. Oil temperature not shown on BC, meaning it's <50 degrees:

 

After 7 hours, probably already on outside temperature, 7-8 degrees:

 

You can see that it changes A LOT. 

Edited 24 November, 2018 by john999boy
Clarification at OP's request.

[Breezy_Pete]

Interesting.  Could you take a photo with a ruler alongside the dipstick, to put some numbers to those level differences, please?

[pist0nbr0ke]

Is part of the difference from 2 mins to 20 mins not down to oil draining back in to the sump from around the engine?

[SuperbTWM]

So who's going to be the first one to get a gallon of Quantum on the hob?

[nidza]

58 minutes ago, pist0nbr0ke said:

Is part of the difference from 2 mins to 20 mins not down to oil draining back in to the sump from around the engine?

 

Exactly. 

 

Still expanded plus drained back. I have probably used incorrect word (settle).

 

This is about the correct point in time to measure the level correctly.

[nidza]

On 23/11/2018 at 21:08, Wino said:

Interesting.  Could you take a photo with a ruler alongside the dipstick, to put some numbers to those level differences, please?

 

I was thinking about your proposal and to repeat the measurement, but I don't think it is necessary as all is frankly clear from the pics. If we agree 20 minutes point is the correct one, cold measuring the oil will cause a measurement mistake of about 30%. I think min-max on the stick is 1 liter, so you can overload the system with 3 deciliters. 

[Breezy_Pete]

I didn't explain well. What I was interested in is how many mm is it between the green lines?

No need to repeat the experiment.

Do you have VCDS? It would be interesting to know how well, or badly, the oil level sensor measurements agree with the dipstick on your engine.

Edited 25 November, 2018 by Wino

[nidza]

I don't have VCDS, but I honestly wouldn't expect that it shows anything different then the dipstick. This one is easy to read, but the old one I had on my ex Alfa was terrible.

 

[Breezy_Pete]

I can think of at least two reasons why the oil level sensor might not agree well with the dipstick.

It may just not be very accurate.

It may not be well temperature compensated, if the system designers decided they don't care if it's accurate when cold for example.

 

On the other hand, it may agree perfectly, and I'll be working with my own car to try to answer that question, I just thought we might both be able to do so, on different engines, which would have been nice.

Anyway, you seem reluctant to cooperate, even to the extent of getting a ruler out to measure the relevant area of the dipstick. I'm not trying to argue with you about your information, I think it's great that you've done this experiment, as you know, I like experimenting.  My car also shows lowest level when cold, so we agree.

Numbers are really useful in science though, so I like to put numbers to measurements, if possible.

Edited 26 November, 2018 by Wino

[TonyD]

Surely the dipstick and sensor are measuring different things. Dipstick is for cold measurement of oil and if requires top up within dipstick limits so volume of oil in the sump. Oil sensor is for low level of oil pressure within the engine which could be requires oil or that oil pup has failed, gasket fail etc. 

[Breezy_Pete]

There's a separate pressure switch for oil pressure. I'm meaning the oil level and temperature sensor in the sump.

Edited 26 November, 2018 by Wino

[ords]

So, should it be checked cold after standing for a few hours , or hot after 10 mins or so to let the oil drain back into the sump?

[gregoir]

Probably tells you in the handbook.

But standing on a flat surface overnight will give the best comparisons, with fewer variables ie not oil temperature or drain down time affected.

[nidza]

3 hours ago, ords said:

So, should it be checked cold after standing for a few hours , or hot after 10 mins or so to let the oil drain back into the sump?

 

VAG (Škoda) isn't exactly precise, but it is telling you to check several minutes after engine is shut off (from the working temperature of 90-100C). 

 

By my findings "several" minutes window is between 10 and 20.

[gregoir]

I take that as the minimum time, if you are in a hurry to check the oil level.

[Ootohere]

Where does one find the instruction saying 'several minutes'.

 

There are VW and SEAT and Audi that might say 'At Operating Temperature' and Normal Operating Temperature, and some Skoda say 'Warm', 

and that is for exactly the same engines.  Usual VW 'Lost in translation'. 

 

 

VW / SKODA / SEAT & AUDI translation to English or American English is 'a few minutes' in manuals. 

& they talk about when fueling the car, so a few minutes is that, not 10-20 minutes.

It is not an HGV that is being fueled.

 

 

 

VW UK as usual can not even give the advice the same in a Video as in a Manual written in English.

She should have checked a Hand Book and not read the script only...

 

 

 

Edited 1 December, 2018 by Offski

[nidza]

20 minutes ago, Offski said:

VW / SKODA / SEAT & AUDI translation to English or American English is 'a few minutes' in manuals. 

& they talk about when fueling the car, so a few minutes is that, not 10-20 minutes.

 

Excuse me for English not being my first language, assuming wrongly 

- a few minutes

- several minutes

 

as same.

 

So, 10 minutes cannot be "a few", as a quote from the user manual ?

 

[Ootohere]

Depends what people consider as several or a few, but that has never been 20 minutes to me unless it is a tea break, then taking a few minutes break might be 30 minutes...

[ords]

Thank you for all the replies

[brettikivi]

in vcds, what's the measuring  block I should be looking at here? We currently have lightly under zero and I'd be interested to see if the level remains consistent according to the level sensor while cooling, never mind the corroboration dipstick / level as read by sensor. Preferably with min / max measurements - I know on the A2 it's expressed as mm, I just don't remember the details.

 

The difference between min and max on a metal dipstick is apparently 0,8l. Assuming that this is a linear progression is not necessarily a good idea, but reasonable. A change of 25% in volume would appear to be not too far off the mark.

 

 - Bret

[gregoir]

Should the withdrawn dipstick be  upside down,  horizontal or remain in the installed direction? All three can be used. I've also had trouble with the level showing differently on both sides. Or being smeared up the dipstick. Diesel and petrol.

Currently,  I check the level on the opposite side to the hatched area.Octavia1.4tsi. This face is revealed when the dipstick is extracted ,rotatatingaround the vertical axis then seems to disturb the level.

I've owned many cars over 40 years,  mostly VW group, and never had this variability.

Edited 2 December, 2018 by gregoir

[Breezy_Pete]

In VCDS its in one or two of the measuring blocks of Instruments module, No.17, if I remember right. 

[Gaz]

Like gregoir, I've had many cars over 38 years of driving.  I've never done anything other than check oil levels on a flat surface, with the engine stone cold, topped it up to max. and I've never had a problem.  Interesting, but I've not really considered it an exact science; over max. = bad, under min. = bad, between min. and max. = good enough.

 

Gaz

[Ootohere]

Here is from the Fabia Mk2 Owners Manual where the 1.2 44kW engine is checked cold and the others when 'warm' according to Skoda.

The Polo Owners manual for these engines said the others should be checked when 'hot' & some manuals said 'at operating temperature.

[shyVRS245]

20 hours ago, Offski said:

Where does one find the instruction saying 'several minutes'.

 

There are VW and SEAT and Audi that might say 'At Operating Temperature' and Normal Operating Temperature, and some Skoda say 'Warm', 

and that is for exactly the same engines.  Usual VW 'Lost in translation'. 

 

 

VW / SKODA / SEAT & AUDI translation to English or American English is 'a few minutes' in manuals. 

& they talk about when fueling the car, so a few minutes is that, not 10-20 minutes.

It is not an HGV that is being fueled.

 

 

 

VW UK as usual can not even give the advice the same in a Video as in a Manual written in English.

She should have checked a Hand Book and not read the script only...

 

 

 

She can drain my fluids anytime.