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racerken

Oil burn with Sustained high speed driving

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Hi,  I recently moved to Germany and I brought along my 997 which was TuV'd in June.  I noticed that after driving high speed/high rpm for sustained time, i.e., 4.5k rpm at 2 hours, burns .5 liter of oil.  I never noticed this in the US because a typical drive to work never exceeded 3k rpm.  

 

997 is stock at 45k miles on the odometer.

 

Thanks.

 

Ken

Edited by racerken

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You finally cooked off all that moisture that had accumulated in your oil. Normal. Monitor your continued usage. It should stabilize.

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7 hours ago, racerken said:

Hi,  I recently moved to Germany and I brought along my 997 which was TuV'd in June.  I noticed that after driving high speed/high rpm for sustained time, i.e., 4.5k rpm at 2 hours, burns .5 liter of oil.  I never noticed this in the US because a typical drive to work never exceeded 3k rpm.  

 

997 is stock at 45k miles on the odometer.

 

Thanks.

 

Ken

In trying to explore the water burn off theory, can you tell us more about your typical trips? Time on the road, time on the road when oil temp was above 200 deg F, trips per week, average ambient temp, etc.

 

0.5 liter of water seems like a lot if you have a non-trivial commute that should be burning it off.

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38 minutes ago, jchapura said:

0.5 liter of water seems like a lot if you have a non-trivial commute that should be burning it off.

That's only about 5%. It's normal. Heck, fuel dilition alone can easily be 2-3%. This is all covered in your owner's manual too, regarding sudden oil level drop. FYI.

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Good point on the water but I'm shocked that you can emulsify .5 liters*water into approx 9 Iiters of oil.  

When the car was in Michigan, my stupid commute was 6 miles all at 30 to 50 mph.  Yes, I know, total waste of a 997 but on weekends I'd blast it on the freeways for 30 minutes.  Oil changes each 6 months, etc.  

In Germany, I typically travel from Stuttgart to Frankfurt which is about 320 miles round trip.  This last trip, i topped off the oil with 1 liter which meant that when I started driving here back in June, I put 5k km's on it with at least 6 to 8 hours of sustained rpm (4.5k rpm sustained, 6k for acceleration but 1 to 2 minutes).

Prior to this last trip to Frankfurt, I topped off to (top of the bars in the instrument panel).  My driving is all Autobahn but in case you didn't know, not all Autobahn is unlimited, there are major intersections which limit speed to 120km/hour or construction which can go down to 60km/hour...  I'd say that 3 hours of very high speed sustained driving with the engine at 4k to 6k rpm all the time.  It's fun but very tiring.  

 

Time on road: 2.5 hours per segment.

Ambient Temp: 27 to 30C

Oil Temp: 225F (even when I cool it off)

trips/week: 2

Gas:  100 Octane

 

There is no visible smoke so I'm assuming that blowby at high rpm, high torque is just a fact of life?  

I guess my new procedure is to keep a close eye on the driving habits vs. oil consumption.

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If there's no oil on the ground and there's no intermix or overheating issue, don't fret ..... and enjoy the freedom of the autobahns to drive as your car should be driven!

Edited by wizard

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I'm pretty sure the Porsche spec is 1 litre per 1,000 km. That's considered normal oil consumption.

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9 hours ago, racerken said:

Good point on the water but I'm shocked that you can emulsify .5 liters*water into approx 9 Iiters of oil...

I'm a little leery too. That seems like a lot of water to see no other symptoms (like the white gooey stuff on the oil cap; or to be seen in the oil filter/cannister at oil change time). Couple that with your state-side driving habit and it really makes it hard to believe (your "at temp time" seem like enough to me). It's probably not all emulsified but being entrained by agitation - separating out quickly when left to stand - probably not a good thing if it's in oiling passageway.

 

I've owned a lot of cars over the years in Texas and upstate NY (think cold in the winter time) and I do not recall ever even thinking about the build up of condensation or blow by water (a byproduct of combustion) in the crankcase. What's the deal with the M9X that it seems to be a water magnet - even to the point of it being called out in the owner's manual - even to the point of influencing the oil level - never seen that before.

 

I guess others have experienced so I've got to get on board with preventing it but sure would like to know even one other make where the issue is as "explicit" as the Porsche M9X.

 

 

BTW, are your tailpipes even a little bit black beyond "normal"?

Edited by jchapura
ask a question of the OP

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update:  the driver side tailpipe does get black.  i do burn 1 liter/1000 km's.

 

When driving around town, there is very little oil loss.  When driving on the autobahn (Stuttgart to Frankfurt @ 200 - 220 km/hr) and I'm downshifting, say 7k down to 5k, i do burn at 1 liter/800 km's.  I recently changed my driving habits to not downshift but rather to use brakes.  Anyway, the burn rate is down to .7 liter/1000 km's.

 

As for the oil loss, it all started after the AOS failure.  perhaps so much oil got sucked in that the rings or something overstressed during the compression stroke? (oil is incompressible). 

Second idea:  I never drove this car as hard as I am now so I'm probably discovering how this monster is really supposed to behave, i.e., goes really fast, drinks oil when driving aggressively.  Makes sense too.

 

If anyone is visiting Stuttgart, be sure to visit the Porsche Museum and this place called Motorworld in Boblingen. PM if you have questions.

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Update:  I gave up and had the motor re-built.  Turned out that the ceramic coating in the cylinder gave way (apparently common here)...  Now it's an Autobahn Screamer for the last 12 months.

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I love mine also. Not very many of them do this but if mine does I'll just have Flat 6 Innovations rebuild the motor and keep going. I think if you own cars like these and use them as your daily driver it helps if you have two of them so when one is down you have the other to drive:)

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