Rickker

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

Jon996

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).

Macster

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.

cdodkin

You simply have a two stroke 996 - very nice

jasper

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.

scubadawg

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.

Rickker

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

jumper5836

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.

s-spiff

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.

ivangene

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)

1999Porsche911

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.

chsu74

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

ivangene

maybe thats it, I not use da mobil 1 stuff

peavynation

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.

Macster

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.