Tracking down high oil consumption; Suggestions welcome

[White987S]

Kevin, you still have it wrong. You need to read through the link.

The 5W50 value is already converted at 4.22.

4.22 is lower than 4.35 (old match and new math!).

This is one of the well known pit falls of an oil with a large range.

[KevinMac]

Kevin, you still have it wrong. You need to read through the link.

The 5W50 value is already converted at 4.22.

4.22 is lower than 4.35 (old match and new math!).

This is one of the well known pit falls of an oil with a large range.

No it's not, that's the problem the Mobil 1 spec sheet specs the 4.22 as non Cst! That's the error LN made! Check out the spec sheet!

BTW here is a synthetic lube fact:

High-quality synthetic oils do not shear back. They have natural temperature-resistant qualities, achieving multigrade

viscosities without the need for unstable polymeric thickeners.

Hence the concern having large spread vis with conventional oils. Can't apply the rule to synthetic.

Just got a response from LN: Here it is!

Here is my note:

Error in your assumptions and tables on your website. You are showing Mobil 1 5w-50 to have a lower HtHS @cst then Mobil 1 0w- 40. The problem is according to the Mobil 1 data sheet the spec for Mobil 1 5w- 50 is 4.22 non cst, not cST. You are comparing the 0w40 through conversion to have a higer HTHS @ cst. Which it does not. So based on the inputs to your conversion factor 5w- 50 has a higher HTHS @cST.

0w- 40

HTHS Viscosity, mPa•s @ 150ºC, ASTM D 4683 3.7

5w-50:

HTHS Viscosity, mPa-s @ 150ºC ASTM D 4683 4.22

You need to correct your table

Here is Charles response!

Thank you Kevin, next update I will make the necessary corrections.

Charles Navarro

LN Engineering

Aircooled Precision Performance

http://www.LNengineering.com

Edited July 30, 2008 by KevinMac

[White987S]

Thanks, Kevin. I talked to Charles this afternoon. He will review his data, and make changes as required. He thinks he possibly double converted the value for the Mobil 0W40.

You were correct.

[Chuck Jones]

Great discussion and even greater resolution between gentlemen who respect each other's views.....and even admit an error. This should be used as a model for how to disagree and resolve in a civil manner.

[KevinMac]

White987s

Thanks! I just wish I could get my hands on the 5w-50, last oil change had to go to 5w- 40 Castrol Syntec. Only reason is SE Florida weather and wanted to stay with oil on the Porsche recommendation list.

Hope we can have more discussions in the future. :thankyou:

Happy motoring! Have a great week!

Edited July 31, 2008 by KevinMac

[Jon996]

OK, i'm adding the barium contrast to the oil today and the car heads in for a CT tomorrow. No fuel after dinner. ;)

Edited July 31, 2008 by Jon996

[perryinva]

I guarantee that the 50 oil in comparison to the 40 oil will have a higher viscosity index @ 100deg C.

viscous = Having relatively high resistance to flow

NOT TRUE!

KevinMac, I was going to make the switch to Mobil's 5W50 until I looked at the HTHS (cSt) numbers.

The 5W50 is a 4.22 vs. a 4.35 for the OW40. So, it looks like the 5W50 has a lower high-temperature high-shear viscosity than the 0w40. I think this is the downfall of an oil with a large range like a 5W50.

I use 5W40 Red Line. The HTHS viscosity is over 5.

I don't know the exat numbers. Most people are under the impression that any X-50 will be thicker than any X-40 at 100C. I don't have the info at my fingertips, but I've taken courses in Tribology, and I thought I remembered that each rating covers an OVERLAPPING range with the next rating. So a 40 could be be thicker than a 50. The viscosity ranges stated are to differentiate the actual formula mix. In GENERAL, narrower speced ranges have better numbers, within the SAME manufacturer. So a 10w-40 will be thicker than a 0-40 and possibly even a 5W-50 at 100C, but would be thinner than a 20W-50 for sure. And a 5W-30 could be thicker than a 10W-40, but not if it is thicker than 5W-50, as that would make the 5W-30 thicker than the 5w-50, and the ranges don't overlap that much. Now, it's been 15 years since I took those courses, and it may not even applt in this case, but I would certainly hope that Porsche would specify the right manufacturers viscosity to use for a reason.

It is also a great misconception that a higher viscosity oil will be burned less or protect better at temperature than a lower viscosity. Viscosity and lubrication quality are totally unrelated. There is a right range and a wrong range, as designed by the engine maker. What IS happening is that if a higher viscosity oil is used and less consuption is observed, it only means that the oil is NOT GETTING TO the places it is needed, and less is used as a result. My professor used to say, he can carry 5 qts of oil in sealed containers in his car trunk and honestly say that his car never uses the last 5 qts. If it's not getting there it isn't doing any good! If you put tar in the crank case, you won't use any either but your engine will sieze. It's all a matter of degree. If an engine is using excessive oil at the viscosity recommended by the manufacturer, then there is something wrong, out of spec, or worn. Now, like I said, I'm not starting a war, and if 5W-50 by a certain manufacturer is recommended, then TRY it. You only have $70 to lose if you change it yourself, and it MAY show you something! I'd still get my oil analyzed by a lab (like Blackstone, about $20)..that will also tell you a LOT!!!

Edited August 1, 2008 by perryinva

[Chuck Jones]

Perry: Interesting perspective, but I have to admit that as I was reading it, I found myself chasing my tail a bit...but then again, my specialty isn't in petroleum products.

It did seem logical that if oil is geting to the right place, it might be consumed at a higher rate than that which doesn't reach the innermost recesses.....but then again, my 930 turbo had been using the Castrol GTX 20-50 and has been running just fine for over 20 years.....I think the compression ratios are about the same for the 996TT (0W-40) and the 930....so I was focused on a lubricant that would be most beneficial for the turbos which spin at an ungodly rate....hence the need to keep the oil clean and changed regularly within the established scheduled cycles.

The dimension I never considered was the actual compositional makeup of the oils and the additives...which truthfully, I still don't understand very well....but this thread has been most revealing and informative for the neophye that I am.

[KevinMac]

Perry: Interesting perspective, but I have to admit that as I was reading it, I found myself chasing my tail a bit...but then again, my specialty isn't in petroleum products.

It did seem logical that if oil is geting to the right place, it might be consumed at a higher rate than that which doesn't reach the innermost recesses.....but then again, my 930 turbo had been using the Castrol GTX 20-50 and has been running just fine for over 20 years.....I think the compression ratios are about the same for the 996TT (0W-40) and the 930....so I was focused on a lubricant that would be most beneficial for the turbos which spin at an ungodly rate....hence the need to keep the oil clean and changed regularly within the established scheduled cycles.

The dimension I never considered was the actual compositional makeup of the oils and the additives...which truthfully, I still don't understand very well....but this thread has been most revealing and informative for the neophye that I am.

Perry - I agree with you when you compare base number as the temp rises Mobil 1 0w- 40 compared to 5w- 50 has a higher viscosity index number at 100 deg C. The discussion was around Mobil 1.

0w - 40

cSt @ 100º C 14

5w- 50

cSt @ 100º C 17.4

[jbrewer]

Greetings again!

I am working with my dealer to track down high oil consumption. It has not reached the value needed for warranty intervention, but is getting close. Car is a 3.6L 996; 2003; about 35K miles.

So far, here is what I can say:

Car seems to run fine . . .

No drips at all.

Quite a bit of soot above left exhaust. Almost small black droplets here and there. Much less on right.

No oil in coolant.

No smoke.

Recently we ran a compression test and a leakdown, both with good results. Compression values varied about 2% between cylinders (210 to 215), and leak down was only 1 to 2 % per cylinder.

I have asked the service team about the AOS, but the absence of smoke makes them think the AOS is OK.

Still under CPO, by the way.

Any suggestions RennTech?

Thanks again!

[jbrewer]

What oil are you using?

Viscosity?

How much oil are you using per a specific number of miles?

oops . . .

Mobil1 0W40

About 1 qt per 600-700 miles. Used to be about 1 qt per 1500 miles. Changed over the winter.

Jon - What did you find out?

[Jon996]

What oil are you using?

Viscosity?

How much oil are you using per a specific number of miles?

oops . . .

Mobil1 0W40

About 1 qt per 600-700 miles. Used to be about 1 qt per 1500 miles. Changed over the winter.

Jon - What did you find out?

Well, thanks for asking! Actually, I am getting kind of tired of looking. . .

So far, had:

Great leakdown results.

Great compression test results.

Changed AOS

Boroscope to check valve seals

Next stop: boroscope cylinders when I change plugs in a few months

Also, just for fun, might simply change to Castrol Syntec 5W-50. Nothing to lose.

42K miles so far, seems to run great, no smoke . . .

Will report back again down the road a bit.

Edited December 17, 2008 by Jon996

[RF5BPilot]

I must think in too simplistic ways. I would have assumed that if you didn't have a leak, you'd see a dark plug (or dark exhaust header).

Edited December 18, 2008 by RF5BPilot

[logray]

All this oil theory...

A little soot on one bank is probably not the end of the world. All of the tests show no problems, aside from pulling your plugs which might show which cylinder is suspect. How much do you abuse your throttle? Someone mentioned a stuck fuel injector. Perhaps it is "unstuck" now? Is soot still accumulating?

My 99 C2 w/56k burns about 1 qt every 4k miles and is guilty of a little bit of soot and burn off over a long period. I've always thought that buring a little oil is a good thing - keeps the oil more fresh? ;-) A little soot is like more wrinkles on your face, or more lines on your hands.

Have you read the owners manual??!!!???? It does say the engine consumes oil.... Especially considering the compression.

[hdarth]

Did you ever figure out what the problem was with your 03. I also have a 03 C4S and I also live in MN and have been driving the car this winter. It has been brutal winter as far as temps go and I noticed that my left exhaust pipe has extra black soot around it and I am also burning oil at a rapid rate. I am running 0W40 and am burning a Qt every 500 miles. It seems to have gotten a lot worse when the weather got cold. It has been between -10 and 0 here off and on for the last month. Does anyone have any more input on what would cause this?

[Jon996]

Did you ever figure out what the problem was with your 03. I also have a 03 C4S and I also live in MN and have been driving the car this winter. It has been brutal winter as far as temps go and I noticed that my left exhaust pipe has extra black soot around it and I am also burning oil at a rapid rate. I am running 0W40 and am burning a Qt every 500 miles. It seems to have gotten a lot worse when the weather got cold. It has been between -10 and 0 here off and on for the last month. Does anyone have any more input on what would cause this?

Thanks for asking! Still working on it, but it is slow. With every tweek, the dealer needs to do an official oil check, which means drop the car off for a day while it cools, pick it up, arrange my schedule so that I can return at 600 miles, then leave it a day so it cools to recheck, then the service manager calls the regional Porsche rep. etc etc.

My history mimics yours--consumption went up after my first winter with the car, and has stayed at the high level. When it warms a little around here I really want to try 5W 50 Castrol (can't get 5W 50 Mobil).

[lancelot092466]

Did you ever figure out what the problem was with your 03. I also have a 03 C4S and I also live in MN and have been driving the car this winter. It has been brutal winter as far as temps go and I noticed that my left exhaust pipe has extra black soot around it and I am also burning oil at a rapid rate. I am running 0W40 and am burning a Qt every 500 miles. It seems to have gotten a lot worse when the weather got cold. It has been between -10 and 0 here off and on for the last month. Does anyone have any more input on what would cause this?

Thanks for asking! Still working on it, but it is slow. With every tweek, the dealer needs to do an official oil check, which means drop the car off for a day while it cools, pick it up, arrange my schedule so that I can return at 600 miles, then leave it a day so it cools to recheck, then the service manager calls the regional Porsche rep. etc etc.

My history mimics yours--consumption went up after my first winter with the car, and has stayed at the high level. When it warms a little around here I really want to try 5W 50 Castrol (can't get 5W 50 Mobil).

Hey Jon

Did you ever resolve this issue? It seems that I might be experiencing the same thing in the same bank of my 02 996C4. Before I bring it to the tech I would like to have an idea of what is going on.

Thanks

Richard

[Jon996]

Hi all:

Long story, with a resolution.

Synopsis:

2003 C4S with CPO purchased a couple years ago with 24K miles.

Oil consumption was at about 1 qt per 2000 miles, but suddenly dropped over the winter (a MN winter--the worst kind . . .) to about 1 qt per 600 miles. Not high enough for action at this time.

Observations: Seemed to run fine, no smoke at any time. Excessive soot from left muffler.

During the summer, I paid for a compression and leakdown test. All cylinders within 5% of each other, and the leakdown max was 2%. Pretty good results, from what I hear.

Consumption increased at the next official check to 1.7 qt in 600 miles. Porsche approved kind of a "leap of faith" change of the AOL. Given the fact I did not have any smoke and the soot was not evenly distributed, we did not really expect this to help, and it did not.

By now, I had 45 K on the engine and was nearing the end of my CPO. I decided to change plugs early, and have the shop bore scope the cylinders and also just examine the plugs. Plug number 6 was pretty sooty, but the piston heads looked clean.

By now, the primary suspicion was leaky valve guides (or is it valve sleeves?). This is a big project to check.

So, I was just about to initiate a new usage test, when I sent an accurate record of the consumption (illustrating the change from purchase) and photos of the soot on the bumper and exhaust. My local manager made quite a few calls (THANKS) and Porsche came up with a plan . . . We would remove the engine and examine the cylinder walls. If they were OK, they would replace the seals. If not, they would replace the engine.

Cylinder 6 was scored, so they replaced the engine. Running great!

[gdalton]

im really concerened after reading this. i reciently purchased a used 2003 c2 with 42,000 miles. i checked the oil level when purchased was full and clean. the last oil change was at posche dealer at 40,000 miles. i checked the oil level today and was at min mark with 42,700 miles. what is AOS? i checked the glossary. it seems that a few other people have a simular problem, surley it is not the motor!!! i also notised the left exhaust is a little blacker and damp when compaired to the right exhaust.

thanks for any advise in advance!

[lancelot092466]

I brought the car into the shop last weekend for the 60K service. I also asked to look into the high oil consumption (1qt/400miles). Well I'm picking up my car from the shop tomorrow. The diagnosis is bad piston rings on cylinder 6. The recommendation is an engine rebuild. For now they say the cylinder sleeves are not damaged and I can keep driving the car, I just need to keep adding oil. I'm really bummed out. I know that a million things could have caused the piston rings to go bad but for future reference, short of doing a borescope prior to buying, what steps could I have taken before buying to foresee this problem? I bought the car used with 52k miles. Also what questions should I ask the shop before dropping another $4k-$8K into this vehicle? I'm not wealthy and money is an issue. This car is my daily driver and I have no other car. So if I do not rebuild it, then it will be bye-bye porsche for quite a long time before I convince my wife again. I truly love driving the car. Has anyone in this community rebuilt their engine and what was your experience. The advice from the community would be greatly appreciated.

Thanks

Richard

[fpb111]

" Has anyone in this community rebuilt their engine and what was your experience. The advice from the community would be greatly appreciated."

Thanks

Richard

Richard,

For one perspective go to Rennlist 996 forum and search for Dharn55. He had a cracked head and pulled & rebuilt his engine. He documented this in multiple threads with pics.