Oil consumption and engine health

[BKC]

I searched but couldn't find a thread related to my question. Can someone give me a run down of oil consumption in the SC and 3.2 as it relates to engine condition? I guess the easy answer is that the more it uses the closer it is to needing major work. How the car is driven would also have an effect.

As a prospective buyer, how will I know how much a car uses? (without having to rely on an owner's word...not talking about you, Jerry! I believe your car is mechanically sound!) The one car I test drove didn't smoke upon start up. After about a 20 min. drive, I held my hand up to the exhaust with the car idling and saw nothing unusual. The tail pipe smelled of warm metal.

I'm just trying to figure out how much oil consumption is acceptable and a way to weed out the ones on their last legs before spending $$ on a PPI.

[DRACO A5OG]

1qt every 1k miles per owners manual

[kidrock]

unfortunately, the best way to find out is the PPI, including a leakdown test. The next best way, and less expensive, is to do a compression test yourself.

[gregwils]

+1 on 1 QT per 1k miles at the lower end.

I would do a leak down and compression, but a leak down won't always reveal higher oil consumption. The valves are closed on a leak down test, so it will tell you that they are seated. It won't necessarily tell you if the guides and/or seals are bad. A PPI by a wrench experienced with air-cooled can pull the covers and tell you if there is excessive lateral movement in the valves - an indication of guide wear/condition.

Actual records will provide the best evidence of oil consumption, but understand your dilemma as a prospective buyer. If I were in the market again, knowing what I know, this is what I would do. I would have the car parked for 24 hours, then be present to start. If there is no oil puff, it's a good indication the valve seals are in good condition. I redid my motor last winter and could park the car for a day, week, etc and no even the smallest puff.

A puff doesn't mean it's bad, but probably take one more step - make that do this no matter what. Take a friend with you, let him drive the car. You follow in yours. When the car is warm, signal him to go to full throttle up to 5k, then let off the gas. If you see a lot of lot of soot coming from the exhaust, then I would be more concerned. There is no full proof method, but if you have someone qualified pull the valve covers, get good compression and leak down, plus no visual evidence in your start and deceleration tests, you should have a lower risk of high oil consumption

[DG624]

"When the car is warm, signal him to go to full throttle up to 5k, then let off the gas."

I was told that this helps to show if the valve guides are worn. A leak down test won't do this. Also an oil analysis can show if there is an unusally high amount of bearing material in the oil (lead, tin, copper...).

[AlfonsoR]

The two visual signs of high oil consumption are: 1) smoke out the exhaust and 2) oil on the spark plugs.

I would recommend that you do PPI at a shop that knows the air cooled engines. If you mention where you are, we might be able to recommend a shop.

A proper PPI should include doing a leak down test. To do a proper leak down, you will need to get the engine to operating temperature. During warm-up of the engine, you can blip the throttle as suggested above, and look for smoke. If it passes that test, then go through with the PPI, and ask the tech to cover inspection of the spark plugs with you.

[craigyirush]

Originally Posted by DRACO A5OG

1qt every 1k miles per owners manual

Actually, the owners' manual (at least for my '86 targa) says one litre/1000 kms which is a lot more than a one quart/1000 miles.

[Peter Zimmermann]

Originally Posted by craigyirush

Actually, the owners' manual (at least for my '86 targa) says one litre/1000 kms which is a lot more than a one quart/1000 miles.

Correct, consumption, according to Porsche, is acceptable down to a quart per 600 miles; but the "norm" that makes most owners comfortable is a quart/1K miles. My shop kept to the rule that if a 911 (this was mostly the case with 3.2 liter cars) reached a consumption rate of a quart/300 miles it was time to take it apart.

The suggestion above, to follow the car and with the engine warm hold the engine at 4-5K revs for a city block, then decel by removing your foot from the gas, is excellent. I've done this a hundred times, and it removes some of the pressure to get an honest answer from a seller (and sometimes a seller doesn't honestly know).

[JCFL]

I am now driving my second Porsche, a 1982 SC, which I've had for one year. Previously, I had a 1984 Carrera with a 3.2 engine. I am by no mean an expert, not at all.

But I can report that my 1984 3.2 had been rebuilt several years prior to my buying it by an expert Porsche mechanic. He must have done an excellent job, because through about 20,000 miles of driving, I averaged about 4300 to 4800 miles per quart.

I once called PCA expert to verify if there was with my engine because of such low oil consumption. He said that I was one of the lucky ones, with such great mileage.

My current Porsche, 1982 SC, has 135, miles on the engine. Last summer, I drove 13,000 miles over 6 months, and my average was about 1 quart of oil per 1600 to 1900 miles driven.

Good luck.

JCFL

[craigyirush]

Originally Posted by Peter Zimmermann

Correct, consumption, according to Porsche, is acceptable down to a quart per 600 miles; but the "norm" that makes most owners comfortable is a quart/1K miles. My shop kept to the rule that if a 911 (this was mostly the case with 3.2 liter cars) reached a consumption rate of a quart/300 miles it was time to take it apart.

The suggestion above, to follow the car and with the engine warm hold the engine at 4-5K revs for a city block, then decel by removing your foot from the gas, is excellent. I've done this a hundred times, and it removes some of the pressure to get an honest answer from a seller (and sometimes a seller doesn't honestly know).

Peter,

Why do you think Porsche specified 600 miles/quart? Would your engine really be OK if it was using that much oil?

[BKC]

Thanks for all the replies.

I live north of Seattle so there are many good air-cooled shops down there. Does it make sense to have a PPI done at a shop where the car is currently serviced?

[teenerted1]

Originally Posted by BKC

Thanks for all the replies.

I live north of Seattle so there are many good air-cooled shops down there. Does it make sense to have a PPI done at a shop where the car is currently serviced?

JW is a very honest wrench. if it is one of his regular customers he should be able to give you a good low down on the car in question. he would know details about the engines history the owner may not be willing to divulge

[HarryD]

If you see 1000-1500 miles/quart you are in a comfortable Range. When I got my car, it was at 600 miles/quart. FWIW, worn valves guides can be very dramatic. My car at 300 miles/quart, as I lift off the accelerator:

[BKC]

Coincidently, a car I'm interested in is maintained by John Walker!

[El_Mecanico]

All air cool engines in nature consume more oil than water cooled engines. Check out someone that owns one. You will find a qt of oil in the door pockets another in the trunk. I believe that air cool engine in design alone having more gap between piston and cylinder liners due to expansion and contraction under heat conditions contributes significantly.

[Drisump]

My car has 90K miles on it (and hasn't been opened up) and does about 3000 miles to the quart, but oddly, when I gear down to pass (I'm told by other tour members) there is a puff of smoke. Since I haven't actually seen it, I don't know what it LOOKS like. I guess it can't be much, considering the miles that I do between quarts. These are potentially very long-lived engines, on a tour last year I ran into a guy (with a 3.2) with 280k miles that had yet to be opened....no valves, guides.... yet, amazing. He had it for the last 100K miles and I can tell you he didn't baby her at all. Cheers