Why is 1000 mi per qt oil considered great for 3.0 sc engine

[tincan]

Originally Posted by craigyirush

I am all for a survey.

Re the factory oil consumption figures - I once asked Bruce Anderson why they were so high (my Carrera manual says something like a liter/1000 kms!).

He said it was probably a worst case scenario - e.g., 150 mph on the Autobahn mile after mile.

When I drove my '88 3.2 (totally original)home to Ireland, after buying in Germany, I put 2.5 litres in during the 2600 km run, none of it at 150mph but some of it at around 135. When I queried the consumption with the specialist who maintained her in Germany I was told this was quite normal. I have since put on about 1200 kms and added no more oil but I have to drive more sedately here because of speed limits and am still only getting comfortable with a lefty in a righty environment.

Noel
'88 carrera 3.2 Venetian Blue

[javadog]

Part of the variation you guys are seeing can be attributed to the way the cars are driven and, to some degree, the type and weight of oil that is used. Use one of these cars on a track, or blast down the autobahn for hours on end, and the oil consumption will be vastly higher than it would if you were poodling around town at 2,800 rpm, on the way to the coffee shop. Usage patterns will make a difference, too. Some of you make lots of short trips and some of you drive the car infrequently.

If your valve guides feel tight and you don't see any smoke after the engine first starts, I'd say quit worrying about oil consumption and be happy.

JR

[RWebb]

poodling around town??

I realize that you are no doubt"living on Tulsa Time" but....

[javadog]

Originally Posted by RWebb

poodling around town??

I realize that you are no doubt"living on Tulsa Time" but....

I didn't say that I was the one poodling around town. I get 700-1000 miles per quart, not the 3-4000 that some of these guys claimed.

Cars are low mileage, too, so that doesn't explain my relatively "high" consumption. Must be something else....

JR

[Miguel Antonett]

Agree with JR

""If you don't see any smoke after the engine first starts, I'd say quit worrying about oil consumption and be happy.""

[RWebb]

A nice escape!

and yes I agree also -- I think the original poster was just curious.

I also think the air cooled/large clearance explanation makes more sense than just horizontal layout.

[jurhip]

I would not rely on most factory recommendations, such as the one stated for a Toyota. They will normally consider high oil consumption rates "OK" as this is partly a financial decision as they may need to perform a repair under warranty.

I think a good running average based on experience is best. And I would not be concerned if it fell below 1000mi/qt. As it gets to 500mi, then I would be a little more concerned and even more annoyed

[billybek]

Originally Posted by jurhip

I would not rely on most factory recommendations, such as the one stated for a Toyota. They will normally consider high oil consumption rates "OK" as this is partly a financial decision as they may need to perform a repair under warranty.

I think we have a winner here!!!
My thoughts exactly... Especially during break in period.

[Formerly Steve Wilkinson]

I add maybe a quart between 5,000-mile oil changes, and I have a twin-plugged, carbureted 3.35-liter modified SC that gets driven enthusiastically whenever I can bear to take this toxic waste site out on the road. But then I built the engine myself.

[schoward]

Approx. 1,800-2,000 miles = 1 quart in my 81SC. Rarely have to add in between 3,000 mi oil changes given the capacity.

[Deschodt]

Mine went from 1qt every 3000 miles 1 qt every 800 miles or so over the course of 10 years and 180000 miles + countless track days. It runs just as well now as it did then, though, it just eats up more oil, so I vote for tired rings and looser tolerances too...

At the end of the day, regardless of the reason why (valves, layout, tolerance), your choice is a $6000 top end rebuild with a 50/50 chance of success (by that I mean some rebuilt engines still eat more oil than others) or adding $3 of oil every now and them ! ;-) Tough choice.... I think I'd still pick adding oil if it were 1qt every 300 miles ;-) as long as performance is there anyway...

Interesting topic as to the cause though....

[SC-targa]

As many have said, our old 911's have light air cooled engines, with very large thermal operating ranges and large thermal expansion.

In addtion, they are older designs created before the EPA regulated HC output. If you've ever seen older ferraris, the smoked prodigiously on downshifts because the valve guider leaked tremendously. The new Ferraris don't because they could never be certified for sale if they did.

My 82 SC with 167,000 miles on the clock uses a qt of oil every 1750 miles or so. A little more when it's hot out, less when the weather is cooler.

Regards,

Jerry Kroeger

[tsiegwart]

75K miles on a rebuilt 3.2 motor.

1 qt every 1000 miles. Somewhere in between the ranges here.

[robert walsh]

Again hard to believe the differences in consumption. Oddly at the start of the post oil consumtion was high, then as the post grew the oil consumtion got very low, now it seems to be lowering somewhat again. That is simply an observation, however there has been no mention , at least I think, to the introduction of synthetic oil to these older engines, many posts talk of increased leaking problems when switched from dino oil, why would not the same pertain to oil consumption?? If the logic is that synthetic oil passes more easily through smaller opennings, would not the same be true with the rings, valves etc.? Also mentioned several times, what is leaked vs consumed, or as porsche owners are they one in the same? I held out on synthetic, but my mechanic changed it with synthetic by accident, charged me for it, but I must say the little dops on the floor have increased.

[craigyirush]

Originally Posted by Deschodt

At the end of the day, regardless of the reason why (valves, layout, tolerance), your choice is a $6000 top end rebuild with a 50/50 chance of success (by that I mean some rebuilt engines still eat more oil than others) or adding $3 of oil every now and them ! ;-) Tough choice.... I think I'd still pick adding oil if it were 1qt every 300 miles ;-) as long as performance is there anyway...

Interesting topic as to the cause though....

I agree - if it pulls strong and doesn't smoke why worry about oil consumption (especially if a rebuild might not improve things that much)

Having said that, I still find it hard to be sanguine about 1 quart every 6-700 miles (even though mine never smokes).

[robert walsh]

Boy, I had to look that one up, "sanguine" translation: cheerfully optomistic.

[Jay Laifman]

But, with the question of why do Porsches do it more than other cars, one answer was the air cooled. A number of people dismissed the horizontal build. But, the way it's always been explained to me, on a verticle or V engine, when the engine stops, all the oil slowly can find its way back down to the bottom. With the horizontal engine, that bottom is often the cylinder itself. So, on every start up, the oil that stayed in the cylinder is burnt to smithereens (and thus that puff). So, the number of starts per mile might have something to do with that, as with the angle of the car when parked. And, maybe even without gravity pulling oil down out of cylinders, there is more there to get past rings to be burned out.

[craigyirush]

Originally Posted by Jay Laifman

But, with the question of why do Porsches do it more than other cars, one answer was the air cooled. A number of people dismissed the horizontal build. But, the way it's always been explained to me, on a verticle or V engine, when the engine stops, all the oil slowly can find its way back down to the bottom. With the horizontal engine, that bottom is often the cylinder itself. So, on every start up, the oil that stayed in the cylinder is burnt to smithereens (and thus that puff). So, the number of starts per mile might have something to do with that, as with the angle of the car when parked. And, maybe even without gravity pulling oil down out of cylinders, there is more there to get past rings to be burned out.

OK, but that wouldn't explain the huge variability in oil consumption seen in this thread - some with low mileage engines are burning more than even the factory allowed amount, while others burn little or nothing in between oil changes.

[Jay Laifman]

Yeah, I realize that. But, to the extent overall the 911s are worse than others, perhaps that's a contributing reason. Since no one described it, I thought I'd throw it out there.

When I recently had my 911 rebuilt, I received quite a bit of information, some of it contradictory about all this. First thing is that when my engine was back together, it was puffing oil smoke on start up and not stopping all that quickly. It ended up being most likely the Deves oil rings, rather than the OEM ones. Once we pulled it apart and put in the new OEM rings, it was much better.

Also, there were some engine rebuilders out there that absolutely insisted that the right way to rebuild a 911 engine was to put it together with the rings/cylinders mostly dry for immediate scoring and seating. They insisted that lube would delay seating, if not prevent it from happening ever. These were some pretty well known, publicly praised rebuilders (not MM!). One is even known for racing engines. Others absolutely insisted it was folly.

So, depending on which of these procedures are followed, the outcome can be largely different. The big question is, who is right?

[robert walsh]

I would like to ask the simple question I posted earlier, were and or are porsche air colled angines mfg approx 25 years ago, truely okay to run synthetic oils in? I agree and have seen the benefits of extra cooling and perhaps lubrication and increased oil longevity, perhaps the tolerances the engines were built with lend them to consume more synthetic oil vs dino oil. Certainly the increased oil spots on the garage floor would attest to that. Logical or way off base?