Quote:
MMD said:
Geez, I can't remember which Rennteamer did this great research and essay. Was it Gnil, or Jim? Anyway, it wasn't I who did this good work. It's a thread somewhere on this board; anybody have the link? Here's the text I copied. I hope this helps.


For my C2S, I have the following oil consumption statistics:

1) the first 1716 miles, I added 650 ml, or about 0.7 quarts;

2) by 2170 miles, or additional 454 miles, I had to add another 400 ml;

3) by 2306 miles, or an additional 136 miles, I had to add another 200 ml;

4) by 3067 miles, or additional 761 miles, I had to add another 200 ml.

5) by 3615 miles, or an additional 548 miles, it looks like I have to add another 200 ml. (I went for a 200 mile drive today and was running the car between 3,000 - 4,000 rpm most of the time).

That makes an estimated total oil consumption of 1,650 ml, or about 0.456 ml of oil consumption per mile traveled. From my data, it appears that oil consumption is declining as my mileage increases. I was told by a friend that it takes longer for the piston rings to seat properly when using synthetic oil. I'll see what its like when the car gets 5,000 miles on it.

When I asked the dealer about oil consumption (at around 1800 miles), I was told that it was within the normal range.

I polled some Rennteamers a few months ago on oil consumption and got about 10 responses. I got a mean consumption of .289 ml per mile. A rough rule is that you can be 95% sure that your oil consumption is normal if it is within two standard deviations of the mean measure. Based on the small sample response I got, that would place the confidence interval between 0 consumption and 0.555 ml per mile. If this is accurate, that puts my C2S's oil consumption within that interval and is normal.

I'll check the responses on this posting and do some simple computations to see if these newer data significantly alter the results I cited above.


I just incorporated the latest responses into the database I collected earlier from Rennteam members who responded to my May 1 post. Here are the results (I updated red911's data as he responded to my May 1 post).

For those who probably don't drive their cars especially hard, the mean oil consumption is 0.273 ml per mile (or 0.171 ml per km). The standard deviation is 0.119 ml per mile (or 0.074 ml per km). To be roughly 95% confident that your car's oil consumption is normal, based upon the 17 responses, it should be between 0 and 0.511 ml per mile (or between 0 and 0.319 ml per km). Again, this is a crude number and the sample size is small, but it seems to make sense.

For those who apparently drive their cars more aggressively (a sample size of only 5), the mean oil consumptin is 0.73 ml per mile (or 0.456 ml per km), with a standard deviation of 0.12 ml per mile (or 0.075 ml per km). To be roughly 95% confident that your car's oil consumption is normal for an aggressive driver, it should be between 0 and 0.97 ml per mile (or between 0 and 0.606 ml per km).

One interesting additional point - it appears that the standard deviation is almost the same for the basic driving mode group and those who drive aggressively. So, aggressive driving increases oil consumption, but the spread around that higher mean level is the same as for those who don't drive aggressively.

All of these results fit in with what my dealer had told me last April when I got concerned about oil consumption by my 911S. Basically, it's normal and it will likely decline considerably once the rings are fully seated, which takes longer for cars using synthetic oil.



MMD, sorry it took me so long to reply on the oil consumption data I tabulated for the team last September. The note below is what I had gathered then.

From mid-September, 2006. "I collected some stats from other Rennteam members and updated them in early July. For 17 responses, I got a mean (read average) oil consumption of 0.273 ml per mile, with a 0.119 standard deviation. This is generally for folks driving moderately. Even though the sample size is small, you could be about 95% confident that if your consumption was between 0 and 0.511 ml per mile it was within tolerances. For those driving aggressively, oil consumption would be a bit higher.

My own consumption stats after 4652 miles (the last time I added some oil) for my 2006 911 S are 2.050 liters, or 0.441 ml per mile. It goes with the car. Ultra high performance engines have fewer piston rings - I'm not sure about the M97 engine that is in the 911S but I suspect it has just 2 piston rings. That usually means you're going to consume some oil, especially when you're pushing the engine to higher revs.

Frankly, my car runs like a charm."

UPDATE ON MY 997's OIL CONSUMPTION. I had the oil and filter changed at 5392 miles on 3 November 2006, having consumed an estimated 2.05 liters. I have run the car more aggressively since then, traveling about 442 miles, and have not experienced any loss of oil. I was told by my salesman that by about 5,000 miles the engine would be fully broken in and would probably not consume much oil, unless I pushed it really hard.

Hope this helps a bit.


Jim