3.2 Oil Consumption. What is yours?

[JJ 911SC]

Being a new owner of an slightly modified 1983 SC... I was worry about my oil consumption, about 1 quart after 2,000 miles (3 months) due to the usual burning smoke upon starting and the dripping (especially when the oil was brand new).

Today, the September edition of Panorama came in and lo & behold in an answer to a question about "1984-89 Carrera horsepower" (pg 81), it's mentioned that the max consumption for a good engine would be 1qt/1000 miles... One less worry.

Cheers

J.J.

[gtc]

Where did they get that figure?
I use 1 qt every 800 miles or so (251k miles on ODO). I don't know where it goes... the engine doesn't seem to smoke ever, but there is some weeping (no drips) under the engine.

[ben parrish]

I doubt very seriously that you are weeping 1 qt every 800 miles. I am sure that the car is burning oil at a slow amount along with the weeping. All cars burn a little oil. My 86 with 120k uses about 1qt every 3k miles; it also has a few weeps.

[healeykit]

A burn rate of 1qt per 1000 miles is what I've heard to be the point you start to watch the engine, however, I think the factory spec is very high, maybe 1L per 500km

[rwest]

Hi,

I've seen 500 miles a quart in several car specs and always thought it was excessive, but I'm sure the automakers have done testing. My 77 only burned a quart on my recent 4000 mile trip, I was thrilled! It has 168,000 miles, but only 75,000 on what must have been a good rebuild. I have only very minor leaking of oil.

Rutager

[RNajarian]

I'm burning 1 quart per 800 miles. Some oil drips. No smoke on start up

[Rot 911]

Even Porsche says 1qt per 800 miles is considered normal. Not sure where Panorama got their numbers.

[gshase]

78 911SC 96k miles NO MEASURABLE AMOUNT OF OIL IN 3000 + MILES oil changes and 8 years of ownership.

[Venetian]

Before top end rebuild-800 miles/qt, after rebuild-3000 miles/qt.

[theiceman]

i have a 78 SC and i can't even change the oil after 5,000km because it hasn't gone down even a quart and it will overflow my pan

214,000km

[m110]

Originally Posted by Kurt V

Even Porsche says 1qt per 800 miles is considered normal. Not sure where Panorama got their numbers.

I think this has been discussed before that this data is from a radical sense of normal. The factory didn't want people doing 125mph runs on the autobahn to think their consumption was excessive. It depends on how you use it. Most people would say that a quart per 1000 is borderline and not normal but acceptable. Healthy new engines that aren't driven like crazy use much less than that. It's relative. Kinda like when the factory says to add 2 psi to the tires for the 959 for sustained driving over 150mph (or something like that, see the thread on the 959 brochure). Right.

[craigyirush]

Pete Zimmerman in his buyers' guide, Dave at TRE (in convo with me), Bruce Anderson in Excellence (and two other mechanics I've spoken to) all say that 1,000 miles/qt. is normal for a 3.2.

Bruce Anderson says 500 miles/qt. is the point at which you should begin to worry.

[Zef]

Around 3K for one quart.....100 K total on engine.

[tomphot]

I'm getting about 1/2 quart for 2,500 miles - my '85 has 68K miles

[jcunning]

My 3.2 is about 550 miles per quart. I guess I get a little smoke on full throttle acceleration. I don't see it in the mirror. People have told me that are following me. I don't see any smoke at idle or startup either.

The back end of the car does get oily.

I will have to get the engine rebuilt at some point, but it runs okay now and it is still fun to drive.

[FA-18C]

I have heard may versions of allowed consumption, and some have their own interpretation, but looking at the factory Workshop Manual for 84-89 Carreras, page 21 (on the PDF file) states allowable is up to 1.5 liters pre 1000km. This is 1.58qts per 621 miles.

Personally I started tracking consumption once I reached a reasonable baseline after getting the car home. The last 500 mile checks I was at 0.4 qts, so likely estimate of half quart or so per the 1000km. I do get a puff of smoke at start up that clears, and had some seepage at the oil return tubes, but after cleaning the lower part of the engine and the ORTs, no leaks... I plan on replacing the return tubes this winter with some other projects.

[GH85Carrera]

Much of it depends on driving style. If you are driving around town, and staying below 5,000 RPM oil consumption will be lower than a cross country drive at 3,500 RPM in the dead of summer in hot conditions, or a day at the track running at WOT most of the day.

[FA-18C]

Glen, agree 100%. It has been frustrating reading some posts where someone states they are using a quart every 800 miles and some weigh in that they are due for an engine rebuild. Especially when that is perfectly on the mark for what is considered by Porsche as typical.

[icarp]

The closer to the full line you maintain your oil level the more oil you will burn.
This is a dry sump system, it does not matter to the tank if you are 1 qt down from full or 4 qt down from full. What will change is the ultimate temp of the oil, less oil means higher average oil temp.
The temperature is spread out over more quarts of oil when their is more oil.
So why is there more oil consumption with more oil? The space needed, in the oil system, that is available for the oil and it's expansion, must also include enough air space for vapor expansion .
If you are meticulous about the oil level at the top you reduce the area for the oil to expand and force more pressure to be exerted in the crankcase and on the rings .
So for a test keep your oil level at or just below the bottom mark on the dipstick.
I think you will be surprised at the reduction in oil usage . You will still have 4 qts of oil above the oil pickup in the oil tank , the engine will not starve for oil.

If this does not make sense just ask to hear a story about some one checking the oil on a cold engine, pulling the dipstick , finding it empty , adding 2 + quarts ahh thats better,
then driving it until the cloud of smoke is so bad that the engine won't run . Oil expansion !
It might even break something.

Just my thoughts
Ian

[FA-18C]

Ian

Great points, and others share your input. This past 950 miles was a baseline for me, and my 0.8 liters is fine, but only added to see how much to get the same level. Plan to let it come down and keep it as you said, just above the lowest marker and monitor.