Engine oil consumption

I purchased my 996 (99C4) two years ago. It was a high mileage car (about 100,000 miles / 160,000 km) but had been well maintained and looked and ran well. I drove it for 10,000 km and never needed to add a drop of oil. Then the engine blew up. After searching around for awhile, I purchased a used 2004 3.6 X51 engine from California and had it installed in my '99C4. This turned out to be a costly marriage, (needed different computer, wiring harnesses, modules, etc, but that is another story). I have now put 6000 miles / 10,000 km on this engine, and have added 4 liters of oil. Average oil consumption has been one liter/2500 km (or about 1 quart every 1500 miles). The engine runs well, has good low end torque, lots of high end power, but why the high oil consumption? It was supposed to be a nearly new engine. It had a leak down test before it was installed in my car, and all was well. I know Porsche says that some oil consumption is normal, but surely this is not normal? Any comments? Are others adding oil like I am? Thanks, ...Rickker

No idea why, but you are not alone . . . There are lots of threads and polls on this and 6speed online and Rentech. Check the 997 site too. I would venture that 1 qt/1500 miles is higher than average, but clearly not out of the ballpark, so to speak. Not high enough to get too worried about (IMHO).

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Normal. That is Porsche says -- in the owners manual -- 1 liter per 1000km is acceptable. I think we all will agree this is not acceptable -- especially if one bought a new car and its new engine continued this oil consumption rate after break in or developed this high an oil consumption at any time -- but this is is the worst case oil consumption that Porsche would (probably) not address. 1 quart every 1500 miles is not abnormally high oil consumption. It is at the higher end of the allowable limit I grant you, but 1 liter/1000km is around 1 quart every 600 miles. Leak down test is a poor test for ascertaining if an engine will use oil. Leak down test just tests each cylinder's ability to hold pressure with its intake and exhaust valves shut and its piston at top of its compression stroke. The cylinder could be scored to all heck down just a short distance down from where the rings end up when piston all the way up on its compression stroke to where the the cylinder on its intake stroke would suck oil like anything through this scoring (grooves) on/in the cylinder wall and a leak down test would not catch this. Could miss it. In fact, the engine could even be missing one or more oil control rings and I don't think a leak down test would catch this. Oil control rings do not have anything to do with compression. In fact compression could be "better" cause with no oil the compression rings would run very wet with oil, which helps sealing, but plays heck with oil consumption. Sincerely, Macster.

You simply have a two stroke 996 - very nice

Yes - I hear reports of excessive oil consumption, but neither of mine were ever an issue, and my buddy is on his second engine in his 2003 model, and the consumption is low on those as well. I think a litre per 1500 km is considered acceptable by most manufacturers. That's what the Ford guys told me back in 1989 when I complained about my brand new 5.0 Mustang.

I use about 1 litre for every 1200 - 1500 km, my Nissan Pathfinder with 167K, does not burn a drop, go figure I'm using Mobil 1 0-40 right now, but when I park my car for winter, I'm going to try Motul 8100 X Cess 5-40 for this next year and see how my oil comsumption is. Especially recommended for engines experiencing mild oil consumption.

Thanks for your comments. The irritating thing about this is, that the original 3.4 engine, with 160,000 km on the odometer, did not consume any oil at all (or at least I did not need to add any in 10,000 km of driving), ran well, had good power, but then came to its sudden end. The replacement 2004 3.6 engine, supposedly with less than 10 hours of running time, and which cost me a small fortune to adapt my '99 car (this is another story) turns out to be an oil burner. Or is it? There is no sign of oil leakage, so I am assuming the oil is going out the tailpipe. Right or wrong, I have always equated that engines that don't consume oil are good healthy engines. Those that burn oil are either old, worn, or otherwise unhealthy. Maybe I am old fashioned. Not much I can do at this point. Thanks for letting me vent about it here on the forum. ...Rickker

I go through a liter in 400 km at the track. I have to check my oil level before every session and usually need to add oil every 2x25 min sessions because the reading has went from full to the minimum level. I think this is extreme consumption but the engine has done this now for 2 track seasons and runs strong. I only noticed the high consumption after getting flashed with the GIAC chip.

I bought my car with the engine already replaced. The engine now has about 40k kms. In the 1.5 yrs I've owned the car, I've done 3 oil changes, ~8k kms per change. I haven't had to add any oil between changes. The level drops 1-2 bars from full on the gauge each interval, but nothing significant.

thats wierd, I have never added oil between changes...occationally the electronic sensor shows a "little" lower in the morning, but then one day later is right back where it was the day before....where are you checking it and what level do you consider "full" (I run a couple bars below the top down to the middle at cold start)

You would be hard pressed to find anyone who burned oil in their car (Porsche or any other car) that did not reduce or eliminate the burning by using virtually any other oil other than Mobil 0W40. So, I would start by moving to a better and higher absolute viscosity oil. It seems like, even tho I have been preaching about the low qualities of protection of Mobil's 0W40 for several years, some still just don't get it.

I burn oil only when I drive my car hard. Then again, I use thicker oil because of my high mileage.

maybe thats it, I not use da mobil 1 stuff

I'm glad to have read this thread. I haven't owned mine long enough to know if it burns any oil, but if it does, I won't be as concerned about it. One thing interesting is that burning oil (even with smoke coming out the pipe to some degree) doesn't necessarily mean you won't pass smog like I once thought. I had a '78 chevy pickup with warn valve guides that puffed out smoke on throttle blips. Had it smogged multiple times, and each time it passed just fine, even with California's two sniffers in the smoking pipe, and one more in the engine compartment. Burning oil should contribute to the hydrocarbon number, but not nearly as much as I thought it would.

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Otherwise "indentical" engines can vary considerably in their use of oil. Heavy oil consumption can be a sign of a worn engine, to be sure, but it is not a 100% infallible sign. It may just be a valve stem seal with exceptionally large (relatively speaking) clearance. The seal might even be cracked or missing. Only an engine tear down could eliminate these and other similar possibilities. High oil consumption can be from the type of use: lots of idling; high rpm use. Overfilling with oil or running oil level too high. In the Porsche engine maybe a bar or two less oil could make a difference in oil consumption. The oil is being consumed cause the higher oil level causes more oil vapor in the crankcase fumes and the removal of this is not as good in this engine thus more oil vapor in the crankcase fumes are routed to the engine's intake where they are burned. Running the oil too long is another possibility: Oil gets overly contaminated with water and unburned gas which lowers the oil's viscosity which makes the oil more fluid which makes it more inclined to foam and this in turn increases the oil vapor content of the crankcase fumes. If the additional gas and water contaminates raise the level of the oil then this just adds insult to injury. If the oil consumption is steady as the miles increase this suggests the oil is not being run too long, but if for instance you're running the oil say 10K miles and you have to add oil after 6K miles, perhaps a 6K mile or even a 5K mile oil change should be considered. (My 02 Boxster with 225K miles drops its oil level a bar or two just around the 5K mark. Its oil consumption is increasing a bit as the oil level used to not drop at all in 5K miles.) Lastly, different oils can have different oil consumtion rates in the same engine. If you can find an oil that meets all of Porsche's oil requirements in a 5w-40 blend vs. using a 0w-40 blend you might try a change or two with the 5w-40 oil and see if the engine's oil consumption changes for the better. Sincerely, Macster.

I have never been much of a reader, but thanks to McMaster I have greatly impoved my reading skills - guess I just never had anything I cared to read before

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+1, Macster has good info. And you HAVE to give props to a dude with 220k+ miles on a P-car.

One thing to keep in mind, and this is in the OM as well, is that 'when driving hard' you're not really burning the oil perhaps, but burning off the moisture content in the oil.

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Holy Catfish, Batman!!! And I thought my consumption of 1 liter per 2500 km was severe. Of course, has been mainly easy highway driving, with some occasional full throttle and high revs. Having said that, I am attending a lapping session on the DDT at Mosport tomorrow, so I will be interested to find out what the consumption is under those conditions. ...Rickker

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Yes, I find the electronic sensor to be quite sensitive. It seems you have to have the car parked in exactly the same level spot to get a true reading. Anyway, my practice has been to add half a liter when the indicator is a the bottom "add" mark. This brings the level up to about the two-thirds full level. Other than at oil changes, I never fill it up to the top mark. ...Rickker

Have you checked to see if you're leaking oil out of the RMS, rather than burning it?

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Thanks, Macster. Overfilling is not an issue, as I am careful to only add half a liter at a time. I am using Mobil 1 0w-40, which seems to be the most popular choice. I do drive my C4 in the winter, so this is the wrong time of year to try a heavier viscosity oil, but I will do an oil change in the spring and see if that makes a difference. However, I don't see why a 5w-40 would improve things, since the viscosity at high temperatures is the same. Maybe I should try a 10w-50, if there is such a product. ...Rickker

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I know of Porsche approved oils in 5W-50 and 15W-50 weights. Maybe there are others? I'm running 5W-50 since I'm in pretty much 90degree+ weather all the time. I don't feel comfortable with the thicker cold-starting weight of 15W. So far so good.

I've been lucky I guess. I've read multiple threads in this fourm and the Cayenne forum about oil consumption, and neither of my vehicles consumes any noticable oil between oil changes.

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Good luck at Mosport, at Mosport my car doesn't see anything below 4000rpm all the way up to redline in a lot of places. I do consistent 1:37's there. Under normal driving conditions I need to add oil every 2 gas tanks.

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Make sure you are a flat level place when reading your oil level. I would get a low oil level reading when getting fuel at a gas station because the place is at a slight incline. I don't know this for a fact but I have heard that our oil pan is fairly wide and flat which explains the readings all over the map.

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It is a bit confusing but a 0w-40 oil and a 5w-40 can differ in their propensity to be consumed by the engine. One point of view and backed with some test data is that 0w-40 oil breaks down and loses its high temperature sheer resistence. At the same time the oil becomes thinner and thus more likely to make it past rings and valve seals and guides and be burned in the engine. A thinner oil is also more likely to foam more readily and put more oil vapor into the crankcase air which can overwhelm the air oil separtor's ability to extract all this oil vapor. As a result the crankcase fumes fed to the engine via the intake manifold contain more oil vapor and this represents oil consumption. I know of no 10w-40 oil approved/recognized by Porsche for use in its modern water cooled engines. There is some info though that suggests Mobil 1 10w-40 oil a better oil than Mobil 1 0w-40 oil. I use Mobil 1 10w-40 "high mileage" oil in my 02 Boxster with (now) 225K miles. I ran 0w-40 for a long time and even 15w-50 oil before 0w-40. In fact I have probably put more miles on my Boxster engine with any of the 3 oils I listed above than most Boxster owners have put on their Boxster engine with any oil. Based on my experience (and other info) a good oil coupled with a reasonable oil change interval will deliver good engine life. (Other info? Motorcycle courier in UK (London area mainly) gets hundreds of thousands of miles from his motorcycle engines and even though he uses the cheaper car engine oils and not the more expensive motorcycle engine oils the fact the oil gets changed every 3000 to 5000 miles -- which can be every week! -- plays a major role in his courier motorcycle engine longevity.) If you have a good feel for your car's oil consumption with Mobil 0w-40 then come next oil/filter change switch to a Porsche approved 5w-40 oil and see if oil consumption changes (improves hopefully) given the same usage/driving style. If it does improve, result! If not at least you know. Sincerely, Macster.

Here is my story... Purchased my 2002 3.6 at 79,000 klms. At 80,000 klm service the Porsche dealer puts in 0-40 Mobil and it uses a litre every 2000 klms, I ask why -- they say "it's ok". I go to a leading independant (who by the way has some of Porsche's Cup Cars in to work on for them) and he says "use Fuchs 20-50 fully synthetic" So I take his advice and now after 20,000 klms cars runs perfectly and is actually very quiet when idling (no more little ticking noises like before) and USES NO OIL. So, am I going to suffer a failed engine if I continue to run an oil Porsche seem to say is way too heavy? Or is this tie up between Porsche and Mobil a "commercial thing"?

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Well, that is most interesting. Up to recently I have been thinking that Mobil 1 is the Holy Grail of motor oils, and 0w40 is the only way to go. Macster has recommended trying a higher viscosity oil and I do intend to do so, but not until next spring, since I drive my C4 during the winter. I am quite amazed at the dramatic difference that you have reported. Maybe you are right about a commerial thing between Porsche and Mobil. However, there are apparently lots of 996s and 997s running out there using Mobil 0w40 and not consuming any oil. Figure that. Thanks for your story. ...Rickker

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I would never advise anyone to use an oil that does not meet Porsche's approved oil list. There is the matter of any warranty coverage being denied if a non-approved oil used. In your car's case though no warranty is in effect. Also, I think -- no promises of course -- but I think you're engine will be fine with the oil the indy used, provided Fuchs oil is a name brand and meets the various standards -- API, SAE, and ACEA -- for spark ignition engine oils. For instance I have a bottle of Mobil 1 0w-40 and Mobil 1 10w-40 next to me. The 0w-40 label lists: ACEA AE, B3/B4; API Service SM/CF (spark M and compression F). The 10w-40 label lists: ACEA A3/B3, A3/B4-04; API SL/CF. The Mobil 1 10w-40 has an ACEA A3/B4-04 classification. The Mobil 1 0w-40 doesn't even have this if I read my oil bottle labels correctly. There is a newer classification: ACEA - 2008; which neither the 0w-40 or 10w-40 oils meet based on its absence from the label. For a bit of additional info on ACEA classification look here: http://www.lubrizol.com/EuropeanEngineOils/A3B308.html and here: http://www.acea.be/images/uploads/pu...ev%20Sep05.pdf However, there have been some reports that some engine rebuilders -- at least one who posts here on occasion -- and the testing they do with oils has found Mobil 1 0w-40 oil not as good an oil as other oils, including other Mobil 1 blends (like IIRC 10w-40). There are reports that Mobil changed the make up of its 0w-40 oil and not for the better. I'm not talking about the cutting back of anti-wear additives (like zinc) but a change that reaches deeper than that. A change that in some experts' minds renders Mobil 1 0w-40 oil a bad choice. Now I like to point out that my 02 Boxster has covered over 225K miles and is on its original engine (with no work ever done on the engine internals -- IOWs the heads have never been off the engine, nor the cases split) and many of these miles (probably 100K or more) has been with Mobil 1 0w-40 oil in the engine. Mobil 1 0w-40 oil has done ok by me and my Boxster. However I must restate that I follow a 5K mile oil/filter changer interval, sometimes changing the oil/filter just before heading out on a road trip and a week or so later upon returning to home changing the oil/filter again cause in the intervening week the car has covered 5K miles. On one trip in particular I covered 5K miles and then had the oil change at a Sacramento Porsche dealer and then continued my journey covering around 8K miles in all over the span of two weeks. But I note your experience is not uncommon. Other Porsche owners have reported using a different oil (even a different brand of oil) and a heavier W weight oil like 5w-40, 5w-50 or 10w-40, or even 15w-50 and reporting less oil consumption, the cessation of small oil leaks/seeps and less engine clatter upon cold start and so far not one has reported any abnormal behavior that might be -- for instance -- the VarioCam hardware reacting unfavorably to the choice of oil. Sincerely, Macster.

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Just so we're clear. If you using Mobil 0w-40 oil and the engine is using oil you can try switching to a 5w-40 oil (and I think even a 5w-50 oil) as long as the oil is on Porsche's approved oils list (look up Mike Focke's web pages and he has a link to a newer (but not the newest I believe) Porsche approved oils list) and see if the different oil helps curb oil consumption. If you want to use an oil that is not on Porsche's approved oil list, like for instance Mobil 1 15w-50 or Fuchs 20w-50 and so on, you're on your own. Sincerely, Macster.