High Oil Consumption

[puddy]

I just did the math and realized i've used 5 litres of Brad Penn in 3641 kms or 728 kms per litre. This seems to be about twice what the regular consumption should be.

The car only sometimes puffs a little smoke when I fire it up, but not everytime. I'd think with that kind of consumption that it would be smoking alot more. My tail pipes have some black in them, but nothing worse than what i've seen on my daily drivers in the past. I have some oil leaks in the "Triangle of death" but not enough to actually drip. Does this all make sense? Any experts have any thoughts on this?

I was planning to do a compression test and leak down over the winter.

[kenikh]

That seems high. Is your motor dry?

I have an Audi that seems to be suffering from the now infamous oil consumption issues on these cars. I don't see any smoke or notice anything while driving it, but it eats about as much oil as your car does, which is silly for a car with 50k miles.

When I have followed my wife driving the car, though, I do see occasional light smoke on acceleration, which I never notice while driving. You may want to (I know, it is hard) to let someone else drive the car while you follow them. Have them do some WOT pulls and see if you can get some tailpipe smoke. If so, you are probably getting ring blowby.

[puddy]

Thanks Kenikh There is some oil on the motor mostly around the backside and covering the tranny. However it doesn't drip. Surprisingly I have not had 1 drip on my garage floor.

I'll get a buddy, who I trust, to drive it and see if I see any smoke.

[klefroid]

Valve stem oil seals? when they get old they let some oil passing the valves...

[jwasbury]

Leakdown test should answer your question definitively.

My 1979 did not smoke on startup or while running, but had 40% leakdown on #6 cylinder. Upon teardown the problem was obvious. #6 piston at some point got excessively hot, and the crown deformed, rings broke and were no longer sealing properly. The car ran great and was the fastest thing I'd ever driven even with the internal issues. The big clue that prompted me to test leakdown was after spending a fair amount of $ on mods, my car would not out pull a relatively less modded car.

Short of the leakdown test, the only symptoms of a problem were: high oil consumption, less than expected performance from modifications, and an exhaust like puffing of smoke from the oil filler (blowby gases from crankcase)

[puddy]

Originally Posted by jwasbury

Leakdown test should answer your question definitively.

My 1979 did not smoke on startup or while running, but had 40% leakdown on #6 cylinder. Upon teardown the problem was obvious. #6 piston at some point got excessively hot, and the crown deformed, rings broke and were no longer sealing properly. The car ran great and was the fastest thing I'd ever driven even with the internal issues. The big clue that prompted me to test leakdown was after spending a fair amount of $ on mods, my car would not out pull a relatively less modded car.

Short of the leakdown test, the only symptoms of a problem were: high oil consumption, less than expected performance from modifications, and an exhaust like puffing of smoke from the oil filler (blowby gases from crankcase)

That's very interesting, I wonder if I may have a similar issue? My car has been tracked a lot and has seen excessive heat at some point. Enough to melt the backside of the rear reflector and left turn signal, also dried out the engine rubber to a solid brittle plastic and burned paint off the inside of the body behind the rear bumper near the turbo. I'll be doing a leak down test soon. And will post results.

[356911930]

Smoke on acceleration will be rings, smoke on deceleration will be valves.

Best of luck,

Rahl

[puddy]

Originally Posted by 356911930

Smoke on acceleration will be rings, smoke on deceleration will be valves.

Best of luck,

Rahl

It does sound like my car needs a complete valve adjustment. I know it hasn't had one for years. Could this be the cause of the extra consumption?

[kenikh]

No, not directly. Cripes, I do mine once a year, regardless of mileage.

[puddy]

^^ hey i'm a newbie Porsche owner and can't take all the blame here, the PO was slacking I guess. I asked if he'd had the valves adjusted since rebuilding the motor, he said no. The motor was rebuilt over 10 years ago! :O It was not driven much in the last 10 years. Having had the car roughly 1 year and doing my research i know that adjusting my valves is an absolute must and something i'll plan to do once year!

[356911930]

Loose valves will not cause higher oil consumption. It would be worn guides or worn seals. In my experience the valves do not need to be adjusted as often as most on this board suggest. (Probably get flamed for this comment) I've never had a valve tighten over time, which would be the worst case scenario. Don't see how this is possible as I have never had any screw tighten over time.

In my experience the valves that become loose have only become loose by .001" to .003" and only make some noise (clatter). At this point I will adjust them.

I have read other posts that have insisted that their valves tightened over time???? I guess the valve stem could stretch but I have never seen this on one of my cars.

Would love to hear more comments from more experienced gearhead types.

Rahl

[Ronnie's.930]

^^^

It is far more common for the valve lash to decrease (tighten) with time on the engine because the valve faces get hammered into the seats by combustion pressure, and thus, the gap between the valve stems and rockers (the lash) decreases. Having the lash increase is far less common. It's strange that your experience has been so different, however - maybe yer car's just freaky like that?!?!

And as far as Kenik measuring/adjusting the lash on a time interval regardless of engine use, well, I can only conclude that he is certifiably insane!

Also, Rahl, you are correct that many people on Pelican measure/adjust valve clearances when it is entirely unnecessary. Like all engine manufacturers, Porsche specifies a variance of plus or minus .002" in clearance - in other words, quite a bit of range.

[Alan L]

The valve clearance is a performance/maintenance issue. Nothing to do with oil consumption. I do mine veery infrequently - have not seen much movement in them.
Alanq

[kenikh]

My rationale is that I know I drive my car about 4K miles a year, so at the end of the year I change the oil and since the oil is coming out, I check the valves. My system is case dependent. It works be stupid to adjust valves on a car driven 500 miles a year...but don't think that applies to most here.

[puddy]

Well either way i've got a compression and leak down test scheduled with a local Porshce expert with in the next 3 weeks. Just after my last DE event of the season. So assuming the motor survives the last DE and depending on our compression test findings, I will check the valves over the winter since I know it hasn't been done in over 10 years and its making some noise. It'll be a fun bonding experience with my car.

Hopefully i'm not having to rebuild my motor over the winter :/

[kenikh]

Your motor sounds reasonably healthy. If leakdown comes back bad, you'll have next steps and decisions to consider, but if worst case is one piston, that's a DIY job you could do over a weekend. But if you see the slippery slope, RUN THE OTHER WAY!!!

[puddy]

Originally Posted by kenikh

Your motor sounds reasonably healthy. If leakdown comes back bad, you'll have next steps and decisions to consider, but if worst case is one piston, that's a DIY job you could do over a weekend. But if you see the slippery slope, RUN THE OTHER WAY!!!

Haha thanks! I've beaten her pretty hard at 5 DE events this season and she hasn't complained one bit other than using alot of oil. I am very afraid of that slope...

[Alan L]

There is a dark hole at the bottom of the slope. It might be one of those celestial black holes. Seems to have enormous gravitational pull. No escape :-)
Alan

[Ronnie's.930]

Ha ha Alan, you said "hole"!!!!

[Alan L]

You 'crack' me up. :-)