Oil Level

[lees]

Have just joined the 993 family with a 1996 Carrera Coupe in Arena Red with 65K and full history, having recently sold my 964.
My local OPC offered a free check over and they changed the belts for me at the same time as they were all looking a little ragged round the edges. On collecting the car, I was advised they'd drained some oil off because they felt it was too full.
However, following a decent 40 mile run and letting the car idle for 5 mins, the cabin gauge wouldn't rise above the "twenty past" level and the dipstick showed halfway between min and max. Even letting the car idle for another 10 mins made no difference.
On querying this with the OPC, I received the following emailed response:
"Driving the car will never allow the oil temperature to rise to the point for measuring, due to the cooling affect by moving through the air. Also, 5 mins is not long enough at idle, we leave them for at least 35 - 45 mins and the OSF wing to be so hot that it is uncomfortable to touch. We are quite happy with the level we have set it to and tend not to use the dipstick as it's not that accurate because of the temperature that has to be hot"
As a result of this answer I'm at a loss to know how you would expect to check the oil level. I tend to use the cabin gauge as a rough guide only, using the dipstick when idling after a decent run.
I'm not a newcomer to Porsche ownership but find the OPC response strange.
Before I reply to them, I would welcome any thoughts.
Regards and thanks in advance
Chris

 

[les richards]

Hmm - I was under the impression (mainly from those with much greater Porsche experience than I) that the gauge was OK as an indication but the dipstick was the only (proper) way to check the oil level. Also, 35 - 45 mins idling? Seems extreme; I always believed 2 -3 mins was enough to allow the oil in the system to get back to the tank. It seems to me that as the pressure drops at idle the needle in the oil gauge rises - surely that's about right, isn't it? The demand for oil from the engine changes the readings for level and pressure at the same time (more or less) - one up, one down.
I agree that the wing does get hot but I've always taken that to indicate that the oil has reached the cooler at the front not necessarily an indication of when to check the level.
Please someone, correct me if I'm wrong!

 

[lees]

Thanks for your response Les.
Up to this point I concur with all you have said and always relied on the dipstick when hot and idling.
Like you, if someone out there knows differently, please tell
Regards
Chris

 

[John Maddox]

I also agree with Les. Gauge is an indication and the dipstick is the actual level. After a hot run I leave for 3 to 5 mins max then dip the stick.

 

[Gordon Attar]

Lees

First your current method of checking the oil level is how it should be done

As long as the car is up to operating temperature is fine, the handbook says "idle for 30 seconds" on a flat surface. I would have thought 35/40 minute idling could be damaging and would cause the car to overheat.

The oil tank holds 11.5 litres the difference between low to high level on the dipstick is only 1.5 litres, so you are probably only half a litre short of full. Personally I prefer to be a bit short of full to allow for expansion of the oil when very hot and for track days.

 

[ras62]

The front wing should be hot before the oil level is checked, just covering the spoiler vents and leaving it on idle for 10 mins will achieve this. Checking at normal running temp is ok as a rough indication, it is simply that when fully hot the level gauge will rise about 20% more.

 

[lees]

Thanks all for your responses.
It's comforting to know that what I've always done seems to be the correct way to check the oil level.
Chris

 

[matthewb]

The porsche 911 has a dry sump system which uses a separate oil reservoir tank, i.e. there's no oil tray under the engine. This means the engine can be lower, giving a lower centre of gravity. A dry sump system also ensures that the engine is not starved of oil when cornering.

What you're measuring with the dipstick and gauge is the level of oil in the oil reservoir tank (I believe - I'm sure someone will correct me!). The reservoir level goes down when oil is pumped out to where it is needed, when it is needed - which is why the gauge goes down when you press the accelerator. After idling for a while (say, at traffic lights) any oil no-longer required is returned to the reservoir, and the gauge goes back up. This is correct behaviour. I guess you'd see the same thing happening on the dipstick, although I've never tried removing the dipstick when running the engine at high revs.

Therefore, to check the oil level (dipstick or gauge) the car must be idling (and warm and on a flat surface). The gauge and dipstick should always tell a similar story - the dipstick being the more accurate, obviously.

My filling technique is to look through the rear window with engine idling and pour slowly while watching the gauge. I stop before the gauge gets to the top. Then I let the new oil settle and warm-up for 2 or 3 minutes. Then I check with the dipstick. Fine tune as necessary. 1.5 litres will take the reading from 'empty' to full.

This is a useful YouTube link from Porsche - the bit you want is at 3:10 - http://www.youtube.com/watch?v=nHTUskjxFW8

M

 

[Guest]

ORIGINAL: matthewb

The porsche 911 has a dry sump system which uses a separate oil reservoir tank, i.e. there's no oil tray under the engine. This means the engine can be lower, giving a lower centre of gravity. A dry sump system also ensures that the engine is not starved of oil when cornering.

What you're measuring with the dipstick and gauge is the level of oil in the oil reservoir tank (I believe - I'm sure someone will correct me!). The reservoir level goes down when oil is pumped out to where it is needed, when it is needed - which is why the gauge goes down when you press the accelerator. After idling for a while (say, at traffic lights) any oil no-longer required is returned to the reservoir, and the gauge goes back up. This is correct behaviour. I guess you'd see the same thing happening on the dipstick, although I've never tried removing the dipstick when running the engine at high revs.

Therefore, to check the oil level (dipstick or gauge) the car must be idling (and warm and on a flat surface). The gauge and dipstick should always tell a similar story - the dipstick being the more accurate, obviously.

My filling technique is to look through the rear window with engine idling and pour slowly while watching the gauge. I stop before the gauge gets to the top. Then I let the new oil settle and warm-up for 2 or 3 minutes. Then I check with the dipstick. Fine tune as necessary. 1.5 litres will take the reading from 'empty' to full.

This is a useful YouTube link from Porsche - the bit you want is at 3:10 - http://www.youtube.com/watch?v=nHTUskjxFW8

M

Can I suggest a slight modification to this (i.e. follow the procedure recommended by Porsche) - warm engine up to full normal temperature, and ensure temperature needle is past first notch (because at this point, oil thermostat is open, and oil flowing to oil cooler). Then you should check oil level with engine running at idle, using the dipstick. If low, add oil with the engine turned off. Add in small amounts of 100 mls if you're not sure, then check again on the dipstick (with engine running).

Opening the oil filler cap with the engine running is not advisable, and you may get very messy!

These cars are great fun to play with & relatively simple, if you follow the recommended procedures in handbook/workshop manual. Much nicer than my Range Rover...arghh, now there's a complicated car [8|]

 

[matthewb]

Very interesting, Roddy.

My Porsche 993 manual says on p81 ...

- ...engine idling at normal operating temperature (oil temperature gauge in the area of the third marking).

- Do not remove the filler cap when the vehicle is on a slant, otherwise oil may run out. (So I guess it's OK to remove the filler cap with engine idling as long as the car is level.)

- Do not pour in more than 0.5 litres at a time. Watch the level rise on the display instrument while topping up engine oil. (So I guess it's OK to use the gauge to get the level about right while the engine is idling.)


The italic text is mine. The underlined text is as per manual.


Where did you get your "procedure recommended by Porsche"? Not that you're wrong, of course. It's just that I don't think my way is wrong either - and I avoid turning the engine on/off and removing/fitting the filler cap every 100 ml.


M

 

[nfearn]

ORIGINAL: lees

"Driving the car will never allow the oil temperature to rise to the point for measuring, due to the cooling affect by moving through the air. Also, 5 mins is not long enough at idle, we leave them for at least 35 - 45 mins and the OSF wing to be so hot that it is uncomfortable to touch. We are quite happy with the level we have set it to and tend not to use the dipstick as it's not that accurate because of the temperature that has to be hot"

May I suggest that you never let the person who wrote the above do anything at all to your car. If the basic principles implicit in the above are so poorly understood yet expressed with such apparent certainty, problems will surely follow.

 

[matthewb]

In the words of Gordon Brown (the well known financial genius), "I agree with Nick".

M

 

[Gordon Attar]

ORIGINAL: matthewb

Therefore, to check the oil level (dipstick or gauge) the car must be idling (and warm and on a flat surface). The gauge and dipstick should always tell a similar story - the dipstick being the more accurate, obviously.

My filling technique is to look through the rear window with engine idling and pour slowly while watching the gauge. I stop before the gauge gets to the top. Then I let the new oil settle and warm-up for 2 or 3 minutes. Then I check with the dipstick. Fine tune as necessary. 1.5 litres will take the reading from 'empty' to full.

Matthew your filling technique is the correct one that the specialist use for topping up the last litre or two and also whats in the handbook.

 

[Guest]

ORIGINAL: matthewb

Very interesting, Roddy.

My Porsche 993 manual says on p81 ...

- ...engine idling at normal operating temperature (oil temperature gauge in the area of the third marking).

- Do not remove the filler cap when the vehicle is on a slant, otherwise oil may run out. (So I guess it's OK to remove the filler cap with engine idling as long as the car is level.)

- Do not pour in more than 0.5 litres at a time. Watch the level rise on the display instrument while topping up engine oil. (So I guess it's OK to use the gauge to get the level about right while the engine is idling.)


The italic text is mine. The underlined text is as per manual.


Where did you get your "procedure recommended by Porsche"? Not that you're wrong, of course. It's just that I don't think my way is wrong either - and I avoid turning the engine on/off and removing/fitting the filler cap every 100 ml.


M

Hi Matthew,

Although the manual may say that you can add oil by looking at the oil level gauge, it is widely known that this is an unreliable method, and it is much better to look at the dipstick when doing this. That's what I was trying to say. I refer to Adrian Streather's book (Porsche 993 The Essential Companion) which states on p102 "CAUTION - The oil level indicator should never be used as the oil level check during an oil fill operation". If I have taken this advisory statement to be based on Porsche dictat, and it is not, then that's my mistake. I know some people have poo poo'd this book, but I still refer to it from time to time in addition to the workshop manual.

However I would personally never rely on the gauge because gauges can stick or give false readings. As an example, I have again, just completed the annual service on my 993, and ran the engine at idle to get it to the correct temp. before checking the level of the new oil. Guess what? The temp gauge was sticky! It was at 7 o'clock steadfastly after 20 mins of idling. I then turned the engine off for 30 secs. Then turned it on again. Temp. needle then immediately went to 9 o'clock! Probably the freezing weather we currently have contributed to that, plus a period of non-use for the car.

To clarify further on the correct idling temperature, this needs to be 70-90degC. This corresponds to 9 o'clock on the temp gauge (needle horizontal), and the oil cooler thermostat has opened by that temperature (I know that's true because Adrian says so []). I have never seen my needle go up to the third marking (I'm assuming this is the one at 10 o'clock), even on the hottest days in the summer, when in stationary traffic jams. Maybe helps that I put a new oil cooler on my car a few years ago & checked the fan is working as well. Sounds rather close to the red area on the gauge for comfort if that's what the manual says [X(]

I'm sure you would get away with following the 'letter' of the manual, but as we all know, there are a number of statements that Porsche made about our cars, which have been the subject of intense debate by very knowledgeable owners and engineers over the years! I for one will always trust the dipstick. Don't start me on Porsche-recommended 18" tyre pressures! Following that advice to the letter ruined a set of rears for me well before their time.

Regarding opening the oil filler cap with the engine running, if Porsche say you can do this, then go for it. I was always taught that this was a "thou shalt not", because of the risk of oil blow-back, and also causing the engine to run lean/unevenly. I'm sure the DME with its closed loop would compensate, but if I wear out my starter motor with a few extra starts a year, that's fine, because that's another fun job to get my grubby paws into. Always loved working on cars in my spare time for my sins!

I hope this helps to clarify what I meant. I'm off to bed now, early start tomorrow, as the R5 folks are having a jaunt around Nth Wales tomorrow [8D]

Roddy

 

[38F3E1]

I always work out how much to add by looking at the dipstick. Follow the standard procedure in the manual to check oil (not the one given by the OPC!) then work out how much to add. As it is 1.5 between min and max it is pretty easy to work out. Then turn off engine and add the amount. I never like to be fiddling in the engine bay with the engine running, too many rotating parts to get caught on IMO.

For what it is worth although the OPC has a strange procedure for measuring the level I also run my car halfway between min and max and never above. My specialist has always filled it to the same level as a matter of practice as well.

Ian.