Oil Usage

[C4S Surgeon]

As y'all know mine has been diagnosed with a RMS leak, taking it in Tuesday. It uses 1qt/1500mi, that may be common but not normal. I've asked them to do a compression check as well, am I being unreasonable? They gave me a little bit of a hassle about that.

Secondly, I have some minor mods to the car(FS Airbox, GHL's, Alum pedals, etc). Should I consider stripping any of that off prior to taking it in to avoid a warranty confrontation, or am I being paranoid?

PS, I'm assuming the worst for the engine.

Edited January 9, 2005 by C4S Surgeon

[magcuda]

1 qt/1500 miles- no problem at all- worry when it stops useing oil, the hassle about compression test is warranty is not going to pay for it, so either they are going to charge you or eat it themselves. the airbox could raise an eyebrow if it comes down to a p***ing match. if your seal area fails the roundness test don't be suprised when they tell you the engine needs to be replaced. :construction:

[C4S Surgeon]

Why would you not worry when it stops using oil?

[1999Porsche911]

Why would you not worry when it stops using oil?

He is either joking with you or has no idea what he is talking about. Although burning as much oil as you do will not effect the engines life as long as you keep putting more oil in, it is both a pain in the *** and not normal. I am sure that the dealer will verbally tell you that it is nothing to worry about, but see if he will acknowledge your problem in writing and state in writing that it is normal.

Bottom line is, is if you are not leaking oil you are burning it and that means the oil is leaking past the rings. That means the rings are not functioning properly as they were designed. Like I said above, it doesn't mean you have a greater chance of engine failure, but it does mean that your engine is not running up to it's designed capacity because of a compression leak. The drop in performance can not be measured by you or me, but cylinder leakage equals less compression which equals less power.

I would have to guess that not all 6 cylinders are burning oil, but maybe just one or to. You might be able to identify which one by looking at the plugs or at least which bank by looking at the amount of soot in the tail pipes.

Edited January 11, 2005 by 1999Porsche911

[Richard Hamilton]

1qt/1000 miles seems like a lot to me. I change my oil every 6000 miles, and don't need any top-ups between changes. Mine is a 60,000 miler.

Piston ring wear could be one cause, but it could also be valve guide wear. If you get a cylinder leakage test done, it would determine if it is one or the other (or both).

[C4S Surgeon]

Well it's at the dealer now, they actually put it in writing, I was shocked. Still, I said I want a commpression check done, bc I don't believe them.

BTW they said it takes at least 1 1/2 days to do a RMS, sounds like BS to me.

Edited January 11, 2005 by C4S Surgeon

[Loren]

An RMS change takes:

4 hours - if they have the parts in stock and the technican is trained.

1-2 days - if they have to order the parts. (why not wait until the parts arrive?).

2 days - 2 months - if they have to (order and) replace the engine.

[C4S Surgeon]

Update; Got it back last night, NO RMS, said the filler tube had leaked R&R done.

Compression check normal.

I don't know if I believe them, so I'll just follow it along I guess.

[1999Porsche911]

Update; Got it back last night, NO RMS, said the filler tube had leaked R&R done.

Compression check normal.

I don't know if I believe them, so I'll just follow it along I guess.

No RMS!!! No wonder you're losing so much oil, Hee hee!

Glad for you.

[C4S Surgeon]

BTW there is a guy on rennlist with a 997S with a documented RMS at 7k.

[Costa]

As far as Burning/consuming oil is concerned - Do you do many short trips in your C4s or tend to take longer trips?

The reason I ask, is that I read in my Porsche 996 manual that many short trips/frequent start-stops etc tends to cause moisture/acids etc to build up which tends to supplement the oil level. Note that most motors will use some small amount of oil over a period of time.

If you are only doing the short trip/frequent start scenario, then the oil level may seem to the user as if it is not changing due to the buildup of moisture/acids etc. replacing the consumed oil...This manifests itself as "my car does not use any oil".

If you then take the same car for a long drive and get the oil up to the correct operating temp, the motor will tend to burn the moisture away and after the drive it will look to the user as if the car has used a substanial amount of oil - but in reality the majority is just moisture etc which has dissappeared and was effectively displacing the correct oil level.

FYI My 996 uses approx. 200ml per 5000Km's or so - I'd say that 1QT every 1500 miles is within the engine's tolerance levels.

1 quart wrt to approx 10litres of engine oil is relatively minor.

[1999Porsche911]

4,000 mile trip in November and did not lose any oil. Drive it daily and do not lose any oil. Don't drive it and do not lose any oil. Most engines DO NOT use 1 quart of oil every 1,500 miles or even 5,000 miles.

[Costa]

4,000 mile trip in November and did not lose any oil.  Drive it daily and do not lose any oil.  Don't drive it and do not lose any oil.  Most engines DO NOT use 1 quart of oil every 1,500 miles or even 5,000 miles.

<{POST_SNAPBACK}>

OOps my mistake.. :eek: 1 Quart = 1.1Litres (approx) - for some reason I had 250 mL stuck in my head...

You are right in that 1 litre of oil every 1500 miles is excessive.

[C4S Surgeon]

So now where does that leave me?

The dealer claims the RMS ain't leaking, no drops on the floor(for now) although it did appear wet at the engine/tranny junction, they attributed this to a filler tube.

They did a compression check, normal.

Driving wise, I do a lot of short trips on the wknd, long daily tripi during the week.

I'm at a loss as to where this freakin' oil is going, they replaced the filler tube, I guess we'll see.

[bavarian]

Count yourself lucky that you dodged the RMS bullett. I trust they know whether it is RMS or not. Since PAG pays for the repair, there is no reason to doubt their diagnosis. The excessive oil consumption (and I think it is) may well have been caused by the filler tube leak. My '04 C4S used a quart in the first 1500 miles during breakin, but has not required any additional oil from 2500 to 7000 miles.

[1999Porsche911]

What filler tube are the talking about? The oil filler tube isn't even close to the tranny/engine junction. Anyway...any leak should have been corrected by the dealer. There should be NO leaks.

Edited January 13, 2005 by 1999Porsche911

[1999Porsche911]

Have you had any idleing problems. If the oil filler tube was leaking, you would have improper vacuum.

[magcuda]

Of course the dealer put the oil consumption in writing, I used to because it is in you warranty book. Porsche motors use oil, plain and simple. I have been working on them since 1979 and that is not going to change. When I left the dealer, as service manager, 3 years ago they were having the same problems that started with the Boxster and are now with 997s. To tell you the truth the last 993s were the best Porsche ever made, and if they continue with the same problems it will remain the best they ever made, even if they need valve guides at 50ka :soapbox:

[1999Porsche911]

Well maqcuda, I better get my car in for service imediately as I have never lost or burned any oil. Nor have 6 of the 7 other guys I run with, nor my previous Porsches. I guess since you are in the service department, you are unaware of those Porsches that run the way they were designed.

You have confirmed my belief that most service managers try to take the easy way out rather than identifying and correcting the problem.

[ar38070]

1500 miles/quart is not excessive oil use for a porsche. I believe 700 miles/quart is considered excessive per the factory. I know you probably do not want to hear it but that is the way it is.

Oil consumption in a flat 6 is considered "normal". Consider that a lot of people see a white puff of smoke at startup. Why is that? Who knows but it is considered normal. (My guess would be that it has something to do with the horizontal nature of the cylinders/pistons and oil seepage while the engin is sitting.)

Oil consumption is not unexpected in a flat 6. Why? don't know, but certainly parts tolerances is part of it. Also break in procedure. Some engines burn oil, some don't. Also driving style is probably a factor i.e how hard and how often you really work the engine.

I would not worry about it unless you 1) smell it, 2) see wetness or oil on the floor, 3) consumption rate increases significantly.

Also what weight oil you use will impact consumption. Everyone wants to use 0w40 because that is the factory fill. That oil obviously is quite thin. It will seep passed seals, rings, etc. more easily and therefore will disappear. Try 15w50 sometime and see if your consumption decreases.

In the mean time just top off the oil every 500-1000 miles.

[magcuda]

you're right tool pants, the flat design of the motor allows oil to collect on the cylinders that are at tdc. the oil gets by the rings and causes the puff of smoke on start up. as the oil gets comtaminated it appears not to "use" oil as the level stays up. a long hard drive will burn off the comtaminates and then the level will lower. 911 motors are a great motor that is very reliable. 12 hr of sebring and 24 hour of daytona prove that.

You have confirmed my belief that most service managers try to take the easy way out rather than identifying and correcting the problem.

for your information i have never "taken the easy way out" I am the guy that fights with PCNA for my customers as a tech and then later when I was service manager. how many service managers spend more time in/under a car then at their desk? the time I lost in the shop I stayed late to fill out reports to PCNA. So sir do not judge me until you know me

[C4S Surgeon]

maqcuda, i appreciate your input, but what should be my next step if any?