Do I need to add oil?
Rennlist Member
Joined: Mar 2006
Posts: 276
Likes: 0
From: Raleigh, NC
The point is not how low, but the fact that when it is flashing, you don't know how low you really are. How low is too low depends on how you are driving the car. For example, around town city speeds with few high speed turns would tolerate a lower level than track driving with high speed sweepers and high cornering forces. The system doesn't differentiate between 1.3 quarts down and 8.5. I don't know the specific answer to your question as to "how low is too low", but am inclined to follow the manual recommendations, especially during warranty. By the way, I have 11,300 miles on my C4S and it has used only 0.5 quart of oil, that being in the first 2000 miles.
Jerry
Jerry
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Originally Posted by Lori
Should I be checking on a cold engine instead?
I check mine every cold start, out of habit. This is how I monitor any consumption if at all.
If you had an oil leak (RMS failure) and didn't notice the oil spot underneath your car before heading out, the cold engine oil check practice will alert you to your serious problem when the oil level will show a significant drop from the previous day's check. That's why I recommend checking it on every cold start - it only takes a few seconds.
Originally Posted by jhbrennan
One question that I've never seen addressed is what really constitutes "low oil".
Consider a 4 cyl engine with a 4 qt capacity, a 1 qt drop is a 25% drop in oil level, yet these engines are capable of running just fine with a 25% loss in amount of oil.
Our engines are likely more sensitive to fluctuations in oil level and so I would not let the oil level get to the point of "flashing segment" without getting some oil in there ASAP - if the manual is to be believed.
Originally Posted by JMAGOLAN
The system doesn't differentiate between 1.3 quarts down and 8.5.
Drifting
Joined: May 2006
Posts: 2,444
Likes: 8
From: Another Ex pat Brit in SoCal
Originally Posted by rcg412
In the 996, you are supposed to check oil when the car is at operating temperature... isthe 997 supposed to be when cold?
http://www.excellence-mag.com/tns.html
They recommend using the 'measure when cold' method - the 'measure when hot' method is more common in older Air Cooled 911's.
Thread Starter
Three Wheelin'
Joined: Dec 2002
Posts: 1,485
Likes: 1
From: San Francisco Bay Area, CA
Thanks everyone for the informative advices. I know this is the right place to ask 
After reading all your replies, (re)reading the manual, (re)checking the oil level display both at cold and warm, chatting with my Porsche mechanic, ....
I added '1/2 quart' of Mobile1 Synthetic 0W40 oil in my car, follow the procedures in the owners' manual. I did it when the engine was cold and the car was level, inside of my garage.
After adding 1/2 quart of oil, the oil level display showed 'one solid bar' at cold (it was 'one flashing bar' below the low line yesterday). I then drove the car on freeway and local roads for about 20 miles. I parked the car back to my garage, rechecked the oil level, and it showed 'one solid bar'.
I guess I will check the oil again tomorrow morning when the engine is cold.
I remembered that when I first took delivery of the car when it was new, it had '2 solid bar' on a cold start, so after 1,500 miles it used about 3/4 to 1 quart of oil during break-in.
Thanks very much, folks. You have been great helps.
With best regards,
After reading all your replies, (re)reading the manual, (re)checking the oil level display both at cold and warm, chatting with my Porsche mechanic, ....
I added '1/2 quart' of Mobile1 Synthetic 0W40 oil in my car, follow the procedures in the owners' manual. I did it when the engine was cold and the car was level, inside of my garage.
After adding 1/2 quart of oil, the oil level display showed 'one solid bar' at cold (it was 'one flashing bar' below the low line yesterday). I then drove the car on freeway and local roads for about 20 miles. I parked the car back to my garage, rechecked the oil level, and it showed 'one solid bar'.
I guess I will check the oil again tomorrow morning when the engine is cold.
I remembered that when I first took delivery of the car when it was new, it had '2 solid bar' on a cold start, so after 1,500 miles it used about 3/4 to 1 quart of oil during break-in.
Thanks very much, folks. You have been great helps.
With best regards,
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Just to shed some light for you and explain your observation of the other day:
If we were right all along in saying that in a cold start all of the oil can be assumed to have fully drained and settled in the crankcase for a true measure of oil level, and that at other times especially when the engine is warm that there should be less oil in the crankcase during a reading because of the assumption that not all of the oil has fully drained, then we should expect your reading to be lower at the "warm-start" and your bottom segment to be still flashing, right?
But it was displaying a solid bar! In contradiction to the logic we just applied, right? Does that mean the electronic gauge in our 997s is that inaccurate? What gives, right? If our electronic gauge is indeed very accurate (and Porsche says it is) then how could there now be more oil in the crankcase if it hasn't fully drained and settled?
Well, the explanation is simple, really. There's a physical property of all materials called the coefficient of thermal expansion, CTE. As materials get heated up they expand by a known percentage for a given temperature range.
For oil, the volumetric percent change in going from 60 F to 212 F is 6.74%, based on empirical values of the CTE.
That means that if you intially had 7.7 qts in your crankcase (9.0 - 1.3) when you cold-started and the segment was flashing (>1.27 qts low) that amount of oil expanded to 8.2 qts (1/2 qt increase!) when your engine warmed up from 60 F to 212 F. We can assume, just for argument, that 8.0 qts was measured by the electronic gauge during your warm-start measurement and that 0.2 qts was still slowly draining down, which would still give you the solid bar reading you observed.
CONCLUSION: You will always have more oil in your crankcase, in terms of volume, when the engine goes from a cold start to operating temperature. That's just a fact of physics. The other fact is that the mass of the oil remains the same - it's just spread out more thinly. This is just another way of saying that the density of a material (mass/volume) decreases with an increase in temperature.
Bottom line: always check your oil level at approximately the same temperature with a consistent amount of return drainage into the crankcase. The best way to ensure this is at a cold start.
Originally Posted by axhoaxho
When I cold-started my car in the morning, the oil level display showed 'only one flashing bar', and when I warm-started my car after lunch, it showed 'one solid bar'.
But it was displaying a solid bar! In contradiction to the logic we just applied, right? Does that mean the electronic gauge in our 997s is that inaccurate? What gives, right? If our electronic gauge is indeed very accurate (and Porsche says it is) then how could there now be more oil in the crankcase if it hasn't fully drained and settled?
Well, the explanation is simple, really. There's a physical property of all materials called the coefficient of thermal expansion, CTE. As materials get heated up they expand by a known percentage for a given temperature range.
For oil, the volumetric percent change in going from 60 F to 212 F is 6.74%, based on empirical values of the CTE.
That means that if you intially had 7.7 qts in your crankcase (9.0 - 1.3) when you cold-started and the segment was flashing (>1.27 qts low) that amount of oil expanded to 8.2 qts (1/2 qt increase!) when your engine warmed up from 60 F to 212 F. We can assume, just for argument, that 8.0 qts was measured by the electronic gauge during your warm-start measurement and that 0.2 qts was still slowly draining down, which would still give you the solid bar reading you observed.
CONCLUSION: You will always have more oil in your crankcase, in terms of volume, when the engine goes from a cold start to operating temperature. That's just a fact of physics. The other fact is that the mass of the oil remains the same - it's just spread out more thinly. This is just another way of saying that the density of a material (mass/volume) decreases with an increase in temperature.
Bottom line: always check your oil level at approximately the same temperature with a consistent amount of return drainage into the crankcase. The best way to ensure this is at a cold start.
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Originally Posted by Lori
If it reads full when cold, will it be overfull when hot?
If there is still oil in the engine that has not fully drained and settled in the crankcase, probably not. But if it has fully drained then, yes, there is the possibility that it will light up the segment above the maximum line, as it happened for me when I changed my oil last summer and took the reading when it was warm and saw that top segment lit.
I don't think it will do any harm, really. I'm sure the engineers were fully aware of that possibility and designed the engine capacity to absorb the increase in volume from heat expansion - they would have been remiss if they forgot about that - D'Oh!
Rennlist Stories
The Best Porsche Posts for Porsche Enthusiasts
Thinking of Buying a Porsche? Do These 10 Things First
Joe Kucinski
Pixar Pals Turned Into 1-of-1 Porsches!
Michael S. Palmer
Theon Goes Full Carbon Fiber With Stunning New Build
Verdad Gallardo
Genius Porsche-Themed Gifts That'll Make Any Dad or Grad Smile
Joe Kucinski
10 Used Porsches Are Selling for Way Too Cheap
Joe Kucinski
Tuner Is Converting Porsche 911s Into Shooting Brakes
Verdad Gallardo
This Coachbuilt Creation Is A Modern Take on the Legendary Porsche 917
Verdad Gallardo
Is This Convertible Cayenne A Steal, Or A Returnless Investment?
Verdad Gallardo
10 Best Non-Flat Six Porsches You Can Buy For Under $100K
Joe Kucinski
Rennlist Member
Joined: Mar 2006
Posts: 6,570
Likes: 89
From: Austin
Originally Posted by OCBen
Good question.
If there is still oil in the engine that has not fully drained and settled in the crankcase, probably not. But if it has fully drained then, yes, there is the possibility that it will light up the segment above the maximum line, as it happened for me when I changed my oil last summer and took the reading when it was warm and saw that top segment lit.
I don't think it will do any harm, really. I'm sure the engineers were fully aware of that possibility and designed the engine capacity to absorb the increase in volume from heat expansion - they would have been remiss if they forgot about that - D'Oh!
If there is still oil in the engine that has not fully drained and settled in the crankcase, probably not. But if it has fully drained then, yes, there is the possibility that it will light up the segment above the maximum line, as it happened for me when I changed my oil last summer and took the reading when it was warm and saw that top segment lit.
I don't think it will do any harm, really. I'm sure the engineers were fully aware of that possibility and designed the engine capacity to absorb the increase in volume from heat expansion - they would have been remiss if they forgot about that - D'Oh!
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Originally Posted by jhbrennan
Wouldn't it be nice to just have the old dipstick? What are the potetnial problems with an overfill?
One thing I neglected in my analysis above is that aluminum also expands under heat, but not as much as oil does, which expands about 35 times more than aluminum alloy, so in comparison the expansion of the aluminum and the resulting minute increase in crankcase volume can be neglected.
I'm not sure about the potential problems with overfilling, though some here have pointed out frothing of the oil if that were to happen. The manual does warn against it, but they never explain what actually can happen.
Seems like a good question to ask a Porsche tech, seems like they might know what can possibly happen and what indications to look for in that event.
Drifting
Joined: May 2006
Posts: 2,444
Likes: 8
From: Another Ex pat Brit in SoCal
Originally Posted by OCBen
Good question.
If there is still oil in the engine that has not fully drained and settled in the crankcase, probably not. But if it has fully drained then, yes, there is the possibility that it will light up the segment above the maximum line, as it happened for me when I changed my oil last summer and took the reading when it was warm and saw that top segment lit.
I don't think it will do any harm, really. I'm sure the engineers were fully aware of that possibility and designed the engine capacity to absorb the increase in volume from heat expansion - they would have been remiss if they forgot about that - D'Oh!
If there is still oil in the engine that has not fully drained and settled in the crankcase, probably not. But if it has fully drained then, yes, there is the possibility that it will light up the segment above the maximum line, as it happened for me when I changed my oil last summer and took the reading when it was warm and saw that top segment lit.
I don't think it will do any harm, really. I'm sure the engineers were fully aware of that possibility and designed the engine capacity to absorb the increase in volume from heat expansion - they would have been remiss if they forgot about that - D'Oh!
I've seen someone cold fill an F40 to the max mark on the dipstick, then have oil pissing out everywhere when the car was warmed up!
F40 is a 12 Liter oil capacity if I remember correctly.
RTFM In that case - There was a cold fill point, that would then lead to the oil being at MAX on the dipstick when at normal operating temp.
Got to be the same idea on the 996/997 - I've seen my cold reading at a couple of bars, and my hot reading at max on the gauge after a decent drive, so the oil is definitely registering expansion on the gauge.
Poseur
Rennlist Member
Rennlist Member
Joined: Nov 2005
Posts: 17,745
Likes: 301
From: Santa Barbara, CA
As I said perhaps a week ago, put in a half quart at a time and just watch and see what happens. If it looks like it needs more, then put it in. I would never add an entire quart or litre to the engine in one shot, even if it is showing low. I think being a little low is better than being a little overfilled.
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Originally Posted by cdodkin
RTFM In that case - There was a cold fill point, that would then lead to the oil being at MAX on the dipstick when at normal operating temp.
Got to be the same idea on the 996/997 - I've seen my cold reading at a couple of bars, and my hot reading at max on the gauge after a decent drive, so the oil is definitely registering expansion on the gauge.
Got to be the same idea on the 996/997 - I've seen my cold reading at a couple of bars, and my hot reading at max on the gauge after a decent drive, so the oil is definitely registering expansion on the gauge.
The funny thing is that I don't see anywhere in the manual where they advise on when to add oil - cold engine or warm engine. They must not consider it to be a major concern, since it seems like in the most silly of things they overkill with the warnings and then kill again.
But you bring up a good point about there should be a cold full mark and a warm full mark - pretty much like when it comes to pressure readings on tires after expansion of the air from heat.
But in a 12 qt capacity engine in going from 60 F to 212 F the expansion would result in only 12.81 qts. That guy must have really overfilled when cold resulting in the oil to spill out like that.
Originally Posted by Edgy01
I think being a little low is better than being a little overfilled.
I think it's just the obsession that most of us have in wanting to see a full condition, and so we shoot for that full level reading.
But really, the full in this case is the MAXIMUM. Which means we should be somewhere between MINIMUM and MAXIMUM, just as we shoot for in coolant level and all other fluid levels - somewhere in the middle.
But the manual is no help here when all it says is:
"Never add more engine oil than required
to reach the maximum mark."
It should be revised to read something like: "Add enough oil to keep the oil level between the MINIMUM and MAXIMUM marks." Followed by the above warning of not exceeding the maximum mark. Especially for these cars that don't come with a dipstick.
Banned
Joined: Feb 2005
Posts: 15,022
Likes: 13
From: Back in the OC
Now that I think about it, the manual is actually misleading with this statement:
"Never add more engine oil than required
to reach the maximum mark."
That statement makes it sound like the 'maximum mark' is the required target to shoot for, doesn't it?
And as such, it's misleading. There must've been something lost in translation from German to English.
If we're correct in our assessment here, that statement should read instead:
"When adding engine oil keep the level below the maximum mark.
DO NOT EXCEED THE MAXIMUM MARK."
"Never add more engine oil than required
to reach the maximum mark."
That statement makes it sound like the 'maximum mark' is the required target to shoot for, doesn't it?
And as such, it's misleading. There must've been something lost in translation from German to English.
If we're correct in our assessment here, that statement should read instead:
"When adding engine oil keep the level below the maximum mark.
DO NOT EXCEED THE MAXIMUM MARK."
Thread Starter
Three Wheelin'
Joined: Dec 2002
Posts: 1,485
Likes: 1
From: San Francisco Bay Area, CA
Just to shed some light for you and explain your observation of the other day:
Quote:
Originally Posted by axhoaxho
When I cold-started my car in the morning, the oil level display showed 'only one flashing bar', and when I warm-started my car after lunch, it showed 'one solid bar'.
If we were right all along in saying that in a cold start all of the oil can be assumed to have fully drained and settled in the crankcase for a true measure of oil level, and that at other times especially when the engine is warm that there should be less oil in the crankcase during a reading because of the assumption that not all of the oil has fully drained, then we should expect your reading to be lower at the "warm-start" and your bottom segment to be still flashing, right?
But it was displaying a solid bar! In contradiction to the logic we just applied, right? Does that mean the electronic gauge in our 997s is that inaccurate? What gives, right? If our electronic gauge is indeed very accurate (and Porsche says it is) then how could there now be more oil in the crankcase if it hasn't fully drained and settled?
Well, the explanation is simple, really. There's a physical property of all materials called the coefficient of thermal expansion, CTE. As materials get heated up they expand by a known percentage for a given temperature range.
For oil, the volumetric percent change in going from 60 F to 212 F is 6.74%, based on empirical values of the CTE.
That means that if you intially had 7.7 qts in your crankcase (9.0 - 1.3) when you cold-started and the segment was flashing (>1.27 qts low) that amount of oil expanded to 8.2 qts (1/2 qt increase!) when your engine warmed up from 60 F to 212 F. We can assume, just for argument, that 8.0 qts was measured by the electronic gauge during your warm-start measurement and that 0.2 qts was still slowly draining down, which would still give you the solid bar reading you observed.
CONCLUSION: You will always have more oil in your crankcase, in terms of volume, when the engine goes from a cold start to operating temperature. That's just a fact of physics. The other fact is that the mass of the oil remains the same - it's just spread out more thinly. This is just another way of saying that the density of a material (mass/volume) decreases with an increase in temperature.
Bottom line: always check your oil level at approximately the same temperature with a consistent amount of return drainage into the crankcase. The best way to ensure this is at a cold start.
__________________
Ben
Quote:
Originally Posted by axhoaxho
When I cold-started my car in the morning, the oil level display showed 'only one flashing bar', and when I warm-started my car after lunch, it showed 'one solid bar'.
If we were right all along in saying that in a cold start all of the oil can be assumed to have fully drained and settled in the crankcase for a true measure of oil level, and that at other times especially when the engine is warm that there should be less oil in the crankcase during a reading because of the assumption that not all of the oil has fully drained, then we should expect your reading to be lower at the "warm-start" and your bottom segment to be still flashing, right?
But it was displaying a solid bar! In contradiction to the logic we just applied, right? Does that mean the electronic gauge in our 997s is that inaccurate? What gives, right? If our electronic gauge is indeed very accurate (and Porsche says it is) then how could there now be more oil in the crankcase if it hasn't fully drained and settled?
Well, the explanation is simple, really. There's a physical property of all materials called the coefficient of thermal expansion, CTE. As materials get heated up they expand by a known percentage for a given temperature range.
For oil, the volumetric percent change in going from 60 F to 212 F is 6.74%, based on empirical values of the CTE.
That means that if you intially had 7.7 qts in your crankcase (9.0 - 1.3) when you cold-started and the segment was flashing (>1.27 qts low) that amount of oil expanded to 8.2 qts (1/2 qt increase!) when your engine warmed up from 60 F to 212 F. We can assume, just for argument, that 8.0 qts was measured by the electronic gauge during your warm-start measurement and that 0.2 qts was still slowly draining down, which would still give you the solid bar reading you observed.
CONCLUSION: You will always have more oil in your crankcase, in terms of volume, when the engine goes from a cold start to operating temperature. That's just a fact of physics. The other fact is that the mass of the oil remains the same - it's just spread out more thinly. This is just another way of saying that the density of a material (mass/volume) decreases with an increase in temperature.
Bottom line: always check your oil level at approximately the same temperature with a consistent amount of return drainage into the crankcase. The best way to ensure this is at a cold start.
__________________
Ben
I chatted with my dealer mechanc. He also agreed that a little less oil is safer than overfilling the oil. He advised that just drive our car until one day the oil level display drops below one bar and then add '1/2 quart at a time' (just on the safe side). Drive the car a couple days, recheck the oil, and add 1/2 quart again if necessary.
Thanks again folks, all great informaton.
With best regards,