Normal oil consumption for 86 Carrera?

[godxilla2]

What is "normal" oil consumption for an 86 carrera?

I am tracking my oil consumption at about 1 qrt every 700 miles on a car i recently purchased.

[Joe Bob]

That would be a lot.....

Done any compression or leak down testing? Did you get a pre purchase inspection?

Does it smoke? Decel, accel, all the time? Gas in the oil?

[Dueller]

3.2 Oil Usage


Quoting the Carrera owner's manual, page 64:

"Engine oil Consumption

It is normal for your engine to consume oil. The rate of oil consumption depends on the quality and viscosity of oil, the speed at which the engine is operated, the climate, road conditions as well as the amount of dilution and oxidation of the lubricant.

Because of these variables, no standard rate of oil consumption can be established, but drivers should expect increased consumption at high speed and when the engine is new."

[Dueller]

Oh yeah...you do know to check oil levels when the engine is HOT (30 minutes of driving or so), while having been idling for 30+ secs on level ground?

I didn't when I bought my first one...lots of unnecessary panic

That being said, if its not fouling plugs, doesn't smoke on accel/decelleration and doesn't smoke EXCESSIVELY on start up after sitting for a bit, or is not leaking excessive amounts, I wouldn't be overly concerned. Petrol based oil is cheap. Below 1 qt/500 milkes, I would begin to plan for atleast a valve guide/seal repair. Probably fine for now...

With a fresh top end, mine is using 1 qt every 800-1200 miles depending on how spirited the driving is.

[godxilla2]

yup - i have been checking after a about 30 min of driving, on level ground in neutral while the car is on.

the car doesnt seem to smoke more than the first couple minutes after a cold start up. No other wierd smoking stuff like acceling or decelerating. Leak down and compression numbers were all very good.

edit: it did have one bad plug during the ppi, but has been driving great sense i replaced it 500 miles ago.

[Joe Bob]

What weight oil?

[godxilla2]

not sure what weight was used by the PO but, he did an oil change just about 2k mile ago, so i have not done another. but i have been adding swepco 20-50

[Dueller]

That start up smoke is 99% fer sure valve guide seals beginning to go. A common problem in the 3.2. I bet its worst when the car has been sitting for a few days...doesn't happen when its been run, shut of for a minute or two then refired?

Not a real threat to hurting the motor...more of a PITA than anything else.

How many miles on the motor? Top end ever been freshened?

[Joe Bob]

Try a straight weight...like 30w. 40w if it's hot. Don't use synthetic.

[Joe Bob]

Originally posted by Dueller
That start up smoke is 99% fer sure valve guide seals beginning to go. A common problem in the 3.2. I bet its worst when the car has been sitting for a few days...doesn't happen when its been run, shut of for a minute or two then refired?

Not a real threat to hurting the motor...more of a PITA than anything else.

How many miles on the motor? Top end ever been freshened?

Sorry, I disagree....start up smoke can be from sitting for more than a couple of days, parking on an incline, slow turning on an incline, ingesting oil thru the intake with a high oil level, etc......

Smoke at decel is a symptom of valve guide wear.....smoke on accel is most likely rings.

[godxilla2]

motor has 93k.

At what point of oil consumption does a top end rebuild become imperative?

[Joe Bob]

When all the mosquitos die in the 'hood due to the smoke or you get tired of filling the oil tank or the plugs foul so much it won't run or start.....or ya get a "hey stoopid" ticket from the cops....%^B

Since you have 12 quarts to play with....it won't likely spin a bearing.....unless you get gas in the oil due to the rings going as well.

[Dueller]

I certainly will defer to your expertise, Mike...I agree on your accel/decel diagnosis. As far as sitting for a few days, do you agree that that may be caused by valve guide wear assuming it is not over filled or am |I totally offbase?

[Joe Bob]

Originally posted by Dueller
I certainly will defer to your expertise, Mike...I agree on your accel/decel diagnosis. As far as sitting for a few days, do you agree that that may be caused by valve guide wear assuming it is not over filled or am |I totally offbase?

Common "quirk" of the 911 and the dry sump.....that 12 quarts of dead dinosaurs gotta go somewhere.

Cold rings can allow a seep of oil into the combustion chamber, leaky oil lines or cam covers can drip a bit on the heat exchangers, oil tank too full and a backflow device missing or defective will allow ingestion at start up....or a combo of all the above....

[Dueller]

As far as the leaks, that is external...I guess I assumed he was talking about smoke out of the exhauast.

BTW...I shared your "woprocket" nomenclature with a buddy who's a Duc afficionado and he busted a gut...

[godxilla2]

mikez - are u saying that a quart every 700 miles is ok then?

[Dueller]

Hey Godxilla....while Mike is certainly more experienced than me (I've only owned these critters for 4 years), I don't think you should be horribly alarmed but that you should keep an eye on consumption, fouled plugs if it becomes frequent, excessive smoking.

I found the following excerpt from Wayne's (owner of Pelican and our gracious host) article elsewhere on this board.

He agrees with me that when it gets beyond a qt every 500 miles you need to start planning for a rebuild...


"Oil Consumption & Smoking

As your engine ages, it will consume more oil. When the engine is brand new, all of the clearances inside the engine are easily filled with a thin film of oil. As the surfaces wear, the clearances enlarge, and oil begins to slip by them. This oil is then burned in the combustion chamber, as it seeps past the valve guides and piston rings. The wider the clearances, the more oil will be burned away. Also, some oils have different viscosities, and tend to burn at a higher rate than others. In general, thinner, lighter-weight oils have a tendency to flow more easily past worn parts in the engine. Use of a heavier weight oil in a tired engine may help to slightly reduce oil consumption.

In addition, excess clearances mean that the oil films that float the crankshaft bearings require more oil to work properly. Looser gap clearances between bearings means that oil flows more easily around the bearing journals. The result is that more oil is required to do the same task, and there is a corresponding drop in oil pressure and an increase in wear. This small drop in oil pressure can sometimes be seen if careful observance to oil pressure readings are taken over the life of the engine. In general, an increase in oil consumption, coupled with a decrease in oil pressure, is a sure-fire sign that the clearances in the engine have increased, and the engine needs to be rebuilt. In addition, the presence of oil in the combustion chamber may have an adverse affect on the combustion process. Oil tends to lower the effective octane rating of the fuel mixture, thus making the engine a bit more prone to harmful detonation.

So how much oil should your 911 engine be consuming? One quart per 1000 miles is about the standard amount for the 911 engine. Newly rebuilt engines with about 5,000 miles on them will usually burn this amount. If your engine is consuming significantly more oil than this, you have a problem. Consumption of two quarts per 1000 miles is certainly cause for concern.

There are two places that the oil can be lost, either past the piston rings, or the valve guides. If the car is excessively smoking, then there is significant oil being burned in the combustion chamber. Air-cooled engines expand significantly when they are run. It’s not uncommon for the entire engine to expand more than 1/8 of an inch side-to-side when heated from stone cold to operating temperature. This means that certain clearances that are designed to be optimum at operating temperature are sometimes not ideal when the engine is cold. Oil seepage when the engine is cold is considered normal. Just about every 911 engine smokes when it’s started, primarily because some oil has seeped into the combustion chamber when the engine was cold. This smoking is not necessarily a sign that the engine needs to be rebuilt. A more accurate test would be to check for significant smoke when the car is completely warmed up.

What smoke should you look for? White smoke is typically caused by condensation in the engine, and is generally harmless when seen on an air cooled engine. Black smoke means that there is a lot of unburned fuel in the combustion chamber that may be a sign that the car is running too rich. In general, blue, sooty smoke is burning oil. If your engine puts out a big puff of bluish smoke when pulling away from a stoplight, it’s probably a sign that the rings are significantly worn.

Worn rings also produce what is known as blow-by. Just as oil can enter into the combustion chamber, exhaust gases can also be blown into the crankcase when the piston fires. Such blow-by, as it is called, often comes out of the crankcase through the crankcase breather hose on the top front of the engine. This hose connects to the oil tank, and the exhaust gases are recirculated back into the engine through the filler neck on the oil tank. On other cars, blow-by is typically funneled back into the air filter through the positive crankcase ventilation valve (PCV).

Worn valve guides can also contribute to oil loss, although typically less than worn rings. In the mid-1970s, Porsche experimented with new types of valve guides that did not last long at all. As a result, many of the 1974-77 engines had to have their guides replaced at about 60,000 miles. Most of these engines have had this repair done, however, if you find that your engine has not, then you can expect that your guides will be well worn. Worn guides not only leak compression, but also can cause the heads of valves to overheat and break off. This is because close valve guide clearances are necessary for proper cooling of the valve. It should be noted that puffs of smoke on deceleration are usually a sign of worn guides and valve seals.

In addition to the oil burned naturally by the engine, your 911 engine can also lose a lot of oil due to leaks. Many 911 oil leaks drip onto the heat exchangers and are burned off by the high heat. As such, sometimes it’s very difficult to gauge exactly how much oil is being burned by the engine, and how much is actually being lost to oil leaks.

Air-cooled engines are infamous for oil leaks. Whether it’s a Porsche 911 engine or a Volkswagen engine, air-cooled owners will fondly describe that burning oil smell that is characteristic of these cars. To be fair, the air-cooled cars must get their passenger compartment heat from heat exchangers that wrap around the exhaust pipes. If there is an oil leak onto these pipes, then the smell of burning oil will waft up into the passenger compartment. This is the reason why many air-cooled owners diligently try to chase down and repair oil leaks in their engines.

The 911 engine can leak oil from one of many different places. Fortunately, many of these oil leaks can be repaired without tearing down and rebuilding the engine. Project 21 from the book, “101 Projects for Your Porsche 911” details all of the common leaks that can be easily fixed without engine disassembly. If your main goal of rebuilding the engine is to fix some of these major oil leaks, I suggest that you read that section first.

There are a few major leaks that cannot be fixed without major engine work. Crankcase parting line leaks require disassembly, as do leaks between the heads and the cam towers. Leaks from between the chain housing and the cam towers also require major disassembly. Many times a leak will appear to be coming from one of these places when in fact it is leaking from a different point that is significantly easier to fix. Wash the underside of the car and track down all of the easy oil leaks before you decide that it’s time for a rebuild. "


HOPE THIS HELPS...

jim

PS: The entire article is at this link and is very informative:

http://www.pelicanparts.com/techarticles/mult_Engine_Rebuild/mult_engine_rebuild-1.htm

[jester911]

1 quart every 700 miles is high. I use about 1/2 quart every 1800 to 2000 miles. I have 86k on it.
It sounds like you have not put many miles on it yourself.

I would drive it a while longer. It could be just the fact that you are driving it more frequently than was driven before.

It is possible the oil consumption will change after being driven a few more thousand miles.

Even it is does keep up the same consumtion, as long as it does not smoke excessively or run poorly it can be driven for quite a few more miles.

As was mentioned before, leaks could be contributing to the consumtion as well.

[tonythetarga]

I always like to start simple and ask some basic questions. One not asked is how full do you fill the oil tank? Ideally, you don't want to exceed the half way mark on the stick showing the top two quart level. If you keep it topped, it might foam over and be directed into the intake until it finds the ideal level in the tank. You might think you're using oil because you keep re-filling to the top of the stick.

[Dueller]

That being said, Tony, what is your approximate consumption?