Tracking down high oil consumption; Suggestions welcome

[Jon996]

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!

[White987S]

What oil are you using?

Viscosity?

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

[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.

[fpb111]

Black soot on one side almost sounds like a "stuck" fuel injector washing down the cylinder wall and diluting the oil.

[PiG]

Black soot on one side almost sounds like a "stuck" fuel injector washing down the cylinder wall and diluting the oil.

Sorry to come in on this thread but how would this affect oil consumption?

I have high oil consumption in my 996 3.6 also and have checked everything.

I too have a sooty tailpipe on one side so sounds like this could be worthy of investigation. I also suspect the MAF needs replacing. I have 81000 miles on the car.

[Loren]

I would try 5W-50 or 15W-50 and see if it makes any difference.

[Jon996]

I would try 5W-50 or 15W-50 and see if it makes any difference.

Just back from a short trip, and wanted to thank you for the suggestion--I think this is a good idea. I have googled quite a bit, and cannot seem to find 5W-50 synthetic in the US. I will keep looking, however. Little afraid of the 15W-50 in our MN climate (unless I just use it from about June through August).

[Topless]

That does sound like high oil consumption. It's got to be burning off somewhere. Any fouled/dirty spark plugs on the suspected bank? My car loses 1 qt per 10,000 miles. 76k on odometer.

[Chuck Jones]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

[Jon996]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

Thanks--down the road, please post your results. I just noticed that Castrol Syntec 5W50 is also on the approved list. This is a little easier to purchase in MN (or on Amazon.com, for that matter!)

Best Regards,

Jon

[Ahsai]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

Thanks--down the road, please post your results. I just noticed that Castrol Syntec 5W50 is also on the approved list. This is a little easier to purchase in MN (or on Amazon.com, for that matter!)

Best Regards,

Jon

As far as I remember, the lastest oil approval list I saw (here in Renntech) only has either 0w-40 or 5w-40. 5w-50 was NOT on the list.

I'm not saying 5w-50 will not work well but could someone please confirm whether it's on the approved list? Thanks.

Edited July 29, 2008 by Ahsai

[Loren]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

Thanks--down the road, please post your results. I just noticed that Castrol Syntec 5W50 is also on the approved list. This is a little easier to purchase in MN (or on Amazon.com, for that matter!)

Best Regards,

Jon

As far as I remember, the lastest oil approval list I saw (here in Renntech) only has either 0w-40 or 5w-40. 5w-50 was NOT on the list.

I'm not saying 5w-50 will not work well but could someone please confirm whether it's on the approved list? Thanks.

Mobil 1 5W-50 has been on the list at least since 2006.

Porsche updates the list yearly (usually in March). We always have the latest update here in the TSB section for our Contributing Members (like you :D ).

[Ahsai]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

Thanks--down the road, please post your results. I just noticed that Castrol Syntec 5W50 is also on the approved list. This is a little easier to purchase in MN (or on Amazon.com, for that matter!)

Best Regards,

Jon

As far as I remember, the lastest oil approval list I saw (here in Renntech) only has either 0w-40 or 5w-40. 5w-50 was NOT on the list.

I'm not saying 5w-50 will not work well but could someone please confirm whether it's on the approved list? Thanks.

Mobil 1 5W-50 has been on the list at least since 2006.

Porsche updates the list yearly (usually in March). We always have the latest update here in the TSB section for our Contributing Members (like you :D ).

Hi Loren,

Thanks for confriming! I see the 5w-50 now in the TSB, there are only two entries iof 5w-50 in that big table, which I missed.

For the wealth of knowledge here, the membership is one of best thing you can buy in life :)

[KevinMac]

Jon: I found a US distributor in northern California and posted the info in the 996TT forum...he sells by the six-pak and is quite reasonable. Hope this helps you.

I'm going to go to the 5 W 50 on my next oil change. I believe Loren said that the Mobil 1 5W 50 is one of the Porsche approved oils.

Thanks--down the road, please post your results. I just noticed that Castrol Syntec 5W50 is also on the approved list. This is a little easier to purchase in MN (or on Amazon.com, for that matter!)

Best Regards,

Jon

As far as I remember, the lastest oil approval list I saw (here in Renntech) only has either 0w-40 or 5w-40. 5w-50 was NOT on the list.

I'm not saying 5w-50 will not work well but could someone please confirm whether it's on the approved list? Thanks.

Mobil 1 5W-50 has been on the list at least since 2006.

Porsche updates the list yearly (usually in March). We always have the latest update here in the TSB section for our Contributing Members (like you :D ).

Hi Loren,

Thanks for confriming! I see the 5w-50 now in the TSB, there are only two entries iof 5w-50 in that big table, which I missed.

For the wealth of knowledge here, the membership is one of best thing you can buy in life :)

Problem is Mobil 1 5w- 50 is not easy to get in my neck of the woods, in fact i don't see

Mobil 1 5W - 50 on the Mobil 1 list.

Yet I do see Castrol Syntec 5w-50 which does say meets European requirments.

[perryinva]

[Not trying to start any kind of flame war here, But unless your car is leaking oil, changing to 5w-50 will most likely do nothing 5w-50 is thicker when cold, so less likely to leak, but is actually thinner when hot than 0-40, according to Mobils spec. I don't know for sure about the Castrol, but in general, you will always get inferior lubrication when you have a significantly higher spread between the cold & hot rating for viscosity, due to the increased viscosity modifiers that have to be added. I know your car is under warranty, but you will just have to break down and DO some investigative work (or pay to have it done). It's not magic, there are only so many places the oil can go. If you are burning that much oil, then you are poisoning the cats and O2 sensors, and an inspection will show that. Leakdown tests only prove there IS a leak around the valve guides, sets or rings when it fails, it unfortunately doesn't prove there ISN'T one when it passes. Inspect the TB, it's easy, fast & free and will eliminate the AOS for sure. What happens to your idle when you take the oil filler cap off AFTER the engine is totally warmed up and in closed loop mode? These are simple things that ANY competant 996 mechanic would do in an hour to at least get you SOME kind of place to start. Pull the plugs on the sooty bank. Compare them to one on the good side. Yada yada yada..the list is long, but easy.

[KevinMac]

[Not trying to start any kind of flame war here, But unless your car is leaking oil, changing to 5w-50 will most likely do nothing 5w-50 is thicker when cold, so less likely to leak, but is actually thinner when hot than 0-40, according to Mobils spec. I don't know for sure about the Castrol, but in general, you will always get inferior lubrication when you have a significantly higher spread between the cold & hot rating for viscosity, due to the increased viscosity modifiers that have to be added. I know your car is under warranty, but you will just have to break down and DO some investigative work (or pay to have it done). It's not magic, there are only so many places the oil can go. If you are burning that much oil, then you are poisoning the cats and O2 sensors, and an inspection will show that. Leakdown tests only prove there IS a leak around the valve guides, sets or rings when it fails, it unfortunately doesn't prove there ISN'T one when it passes. Inspect the TB, it's easy, fast & free and will eliminate the AOS for sure. What happens to your idle when you take the oil filler cap off AFTER the engine is totally warmed up and in closed loop mode? These are simple things that ANY competant 996 mechanic would do in an hour to at least get you SOME kind of place to start. Pull the plugs on the sooty bank. Compare them to one on the good side. Yada yada yada..the list is long, but easy.

Don't know where you got the info on Mobil 1 5w-50 it's not on their website

5w - 50 is more viscous than 0w-40 when hot and more viscous then 0W- 40 when cold.

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

BTW - if a leak is evident with 0w-40, i can reasonably say it will also leak with with 5w-50

Edited July 30, 2008 by KevinMac

[Loren]

Where to buy Mobil 1 5W-50 in the US (thanks to Chuck Jones)

Distributor for Mobil 1 5W 50

[White987S]

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.

[Topless]

Yes, 5w50 oil may slow the oil consumption but won't solve the problem. 1qt in 700 mi is a lot of oil burning through one bank. A compression/leakdown test should rule out bad rings. Sooting in one bank only should rule out the AOS. Maybe a bad valve guide that is gushing oil when the valve is open. I would still want a look at the plugs on the suspect bank. Something is not right and we don't want the motor to go all shrapnel on us one day. There are only 3 cylinders on that side. One of them is in trouble. Have a closer look.

Edited July 30, 2008 by Topless

[KevinMac]

White 987s - Better go check the facts again:

The vis index at 100 deg C for 5w- 50 is 17.2, 0w- 40 is 14

0w- 40

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

5w-50:

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

So my comments stand

[White987S]

White 987s - Better go check the facts again:

The vis index at 100 deg C for 5w- 50 is 17.2, 0w- 40 is 14

0w- 40

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

5w-50:

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

So my comments stand

No need to re-check. I stand by my comment too.

My source is Charles Navarro, LN Engineering, dated 7/26/08.

What is your source?

http://www.lnengineering.com/oil.html

[KevinMac]

White 987s - Better go check the facts again:

The vis index at 100 deg C for 5w- 50 is 17.2, 0w- 40 is 14

0w- 40

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

5w-50:

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

So my comments stand

No need to re-check. I stand by my comment too.

My source is Charles Navarro, LN Engineering, dated 7/26/08.

What is your source?

http://www.lnengineering.com/oil.html

White 987S -

Since 5w- 50 is not on the Mobil 1 site the 5w-50 quoted above is from the same source you used. BTW the spec for the 5w- 50 is the same you quoted. The 0w- 40 which is wrongly cited by you is right from Mobil 1 spec sheet! Go to the Mobil 1 site and download the sheet! Stand behind it all you want! But I would ascertain that the Mobil 1 spec sheet for 0w- 40 is correct!

http://www.mobil.com/USA-English/Lubes/PDS...bil_1_0W-40.asp

Edited July 30, 2008 by KevinMac

[White987S]

White 987S -

Since 5w- 50 is not on the Mobil 1 site the 5w-50 quoted above is from the same source you used. BTW the spec for the 5w- 50 is the same you quoted. The 0w- 40 which is wrongly cited by you is right from Mobil 1 spec sheet! Go to the Mobil 1 site and download the sheet! Stand behind it all you want! But I would ascertain that the Mobil 1 spec sheet for 0w- 40 is correct!

http://www.mobil.com/USA-English/Lubes/PDS...bil_1_0W-40.asp

Kevin, did you read throught the link (long...I know!). Here is an excerpt from Mr. Navarro:

"I have included the HTHS viscosity - Mobil 1 0w40 is 3.7 cP (3.7cP * 1/.85 specific density = 4.35 actual HTHS in cSt; using the estimate of 14 * .322 yields an estimated 4.50 HTHS, which is off by only 3.4%). If there is a ~ in front of the HTHS, then it's estimated by taking the viscosity at 100C * .322 (this conversion has an R^2 value of 94%). If the actual HTHS was not available, I have shown the estimated value range for the HTHS. All the below oils have Porsche Approval and meet ACEA A3/B3 specifications. The Mobil 1 0w40 is shown for reference only and is not my oil of choice."

So, as you can see, there is a conversion factor that is used for the proper comparison. You are not using apples-to-apples data. This is where you are going wrong.

[1999Porsche911]

Don't confuse "resistance to flow" as "less flow" :rolleyes:

[KevinMac]

White 987S -

Since 5w- 50 is not on the Mobil 1 site the 5w-50 quoted above is from the same source you used. BTW the spec for the 5w- 50 is the same you quoted. The 0w- 40 which is wrongly cited by you is right from Mobil 1 spec sheet! Go to the Mobil 1 site and download the sheet! Stand behind it all you want! But I would ascertain that the Mobil 1 spec sheet for 0w- 40 is correct!

http://www.mobil.com/USA-English/Lubes/PDS...bil_1_0W-40.asp

Kevin, did you read throught the link (long...I know!). Here is an excerpt from Mr. Navarro:

"I have included the HTHS viscosity - Mobil 1 0w40 is 3.7 cP (3.7cP * 1/.85 specific density = 4.35 actual HTHS in cSt; using the estimate of 14 * .322 yields an estimated 4.50 HTHS, which is off by only 3.4%). If there is a ~ in front of the HTHS, then it's estimated by taking the viscosity at 100C * .322 (this conversion has an R^2 value of 94%). If the actual HTHS was not available, I have shown the estimated value range for the HTHS. All the below oils have Porsche Approval and meet ACEA A3/B3 specifications. The Mobil 1 0w40 is shown for reference only and is not my oil of choice."

So, as you can see, there is a conversion factor that is used for the proper comparison. You are not using apples-to-apples data. This is where you are going wrong.

Well if you use the above formula take the 5w-50 @ 4.22cp *1/.85 = 4.96 actual HTHS in cST. So it still shows the 5w- 50 at temp to be higher. The higher the value of HTHs non cst based on the above formula will produce a conversion of a higher Cst rating.

So since the conversion factor is a constant the only difference going into the conversion is the non cST number which is what I have stated! The outcome is still higher for the 5w- 50. The problem is in the table LN lube stated. The HTHS @cST value of 4.22 for 5w- 50 L&N lube stated is incorrect! LN is saying the 5w- 50 is rated at 4.22 @cst, but the Mobil 1 spec sheet shows it as non cST, of which Mobil 1 specs 0w- 40 HTHS non cst. So the LN data seems to be incorrect.

Morale of the story be careful what you read!

I just sent an EMAIL to LN showing their error.

Edited July 30, 2008 by KevinMac