Where is my oil going?!

[Sandspider]

Well, like the title says, since I replaced my oil filter and oil at the end of last year (1986 Lux), oil consumption has increased dramatically. I wasn't measuring it carefully, but I have done so recently and it's 1l oil per 200 - 300 miles! It started when I used fully synth 10W40 rather than semi synth, so I'm topping up now with semi synth, but so far it doesn't seem to have helped. (I've probably topped up around 4l since the initial oil change)

The baffling thing is, I can't figure out where the oil is going. It's not leaking out when the car is startionary - the block and my drive are dry as a bone. It's not burning - my exhaust is clear, smells sweet(ish) and is filled with flapping butterflies, not black smoke. I assumed it might perhaps be leaking out under high pressure acceleration, or when hot... But just now I topped up the oil to a smidgen below the max mark on the dipstick, and ran the car on my drive for 5 or 10 minutes with a bit of revving from time to time to simulate driving. (Fan came on twice, and went off again each time) Not a drop of oil emerged from anywhere, but the mark was a smidge lower on the dipstick when everything had cooled down and dripped back into the sump. (I know, the dipstick is not totally accurate etc., but oil is definitely going somewhere). At cold idle oil pressure is 5 bar. Under acceleration, 5 bar again. At warm idle usually 4.5 - 5 bar, but can decrease slightly towards 4 bar as my oil level decreases. Baffled! [&:]

Does anyone have any thoughts / suggestions as to where my oil is going, or what I should do next to find out?

Many thanks in advance...

Giles

 

[evoboy69]

My car uses oil but I've been told it's not excessive. Driven gently my car doesn't use much but when driven hard it burns it.

It's hard to actually see it unless you're following someone giving your pride and joy full beans!

 

[Alexw]

Tis clearly the engine pixies!

Well, logic says if its disappearing from the dipstick its going SOMEWHERE. SO, get the car up in the air and take the engine pan off to check it for any oil. Also check around the exhaust, it could be leaking onto the exhaust and burning away, but I'd of thought you'd smell that. I recall someone saying something can leak at the back of the engine and be blown onto the exhaust back there, balance shaft gasket maybe? I'd go for it burning away as a little bit of oil goes a long way, so that much you'd see on the floor.
Other option is internal leakage, you may not be able to see the smoke, mine uses oil for sure and even just below redline I can't see any. Check the exhaust pipe itself with a rag, has it got black stuff built up inside?
Taking a break and coming back with a fresh, clear mind often helps me. You get too caught up in the problem and need to take a step back - Can't see the trees 'cause the forest is in the way!
As I said, oil doesn't just disappear - so its going somewhere. Its just hiding itself quite well []

 

[Sandspider]

Porsche tolerances state oil consumption of less than 1l per 1000 km. I'm not getting anywhere near that!

I do indeed blame the engine pixies... There's a bit of black in my tail pipe, but I thought that was 20 years of carbon deposits? If oil was burning as such a rate, surely I'd see it at idle, or smell it, or see it in my rearview mirror at speed? (I don't drive the car particularly hard...) Perhaps I'll give the old brain a rest for a few days, and get someone to follow me when I'm pushing it hard and see if that makes a difference. [&:][]

 

[zcacogp]

The under-trays can hide the underneath of the engine quite well, and they may not be helping.

Try taking them off (both, if they are both still there - one is often missing), and clean the big lumpy bits with a steam cleaner, or jetwasher. Drive for a while, and then have a look. It's much easier to spot oil leaks on a clean engine.

(Although I'll admit that if it has got through that much oil I would expect you to notice where it is coming from by now ... )

Keep us posted.


Oli.

 

[944 man]

ORIGINAL: Sandspider
Does anyone have any thoughts / suggestions as to where my oil is going, or what I should do next to find out?

Yes. Bite the bullet and remove the current oil, and replace it with some good thick 20w-50. Fill it up to the full mark on the dipstick and monitor your useage. This is the only that youre going to e able to identify where its been going.

Different engines (and model years!) react differently to different grades. Many cars struggle with synthetic oils or 10w or 5w grades. My old series one car doesnt use a drop of Silkolene Pro-S 5w-40, but Ive lost one bar of pressure across the range. I have another later car (with essentially an S2 engine) which started using Mobil 5w synthetic like there was no tomorrow: two litres of oil per tank of fuel IIRC! By reverting to a good thick oil mineral youll be able to establish whether the engine has a problem, or whether thin synthetic oild simply dont suit it. Im not going to make you any promises, but Id expect your oil useage to drop significantly as soon as you revert to Castrol High Mileage or something similar.

Simon

 

[**Gareth**]

I had exactly the same problem about a month ago, Just before i purchased the car the previous owner had changed the oil, but i wasnt sure what oil he used to fill it. I was topping it up using semi-synthetic but wasnt really seeing any change. After a getting a bit of advice from some of the guys on here i decided to drain the oil and replace it using 15-40w, Since then ive covered around 200 miles and the level is still on the maximum mark.

 

[Sandspider]

Thanks for the additional suggestions all. Trying to put off removing the undertray while it's raining, but it does sound like thicker oil may be the way forward. Gareth, was your 15w40 semi synthetic, or mineral? And have you noticed a change in oil pressure since the change?

Cheers again,

Giles

 

[944 man]

By reverting to a 15w or 20w mineral youre ruling out two problems at once.

 

[zcacogp]

Well I have to say the oil level on these things confuses the heck outta me. I just looked at the level on mine, and discovered that it has gone UP since I last looked.

Last time I checked was a week or so ago. The warning light had started coming on if it was started from cold, then stopped and re-started within 10 minutes or so. (I am guessing because the oil is sucked up to the top of the engine, and then drains down to the sump again. Being cold, it drains slowly.) I checked, and it was about 1/2 - 2/3 of the way down the dipstick. (That check was done about an hour after turning the engine off.)

This time it had been left overnight. I checked, and it was only about 1/4 of the way down! I topped it up (about 1/4 of a litre, possibly less) and it is back on the top mark. I know that the warning light starts to show when it gets to about 1/4 empty, so I guess this simply confirms what I already know (and also proves that it can take a very long time for the oil to get from the top of the S2 engine to the bottom.)


Oli.

ETA, should anyone wonder, that is the first top-up in around 2400 miles since a service, when it was last at the top mark. 10W40 semi oil.

 

[944 man]

ORIGINAL: sc0tty

Why would anyone put fully synthetic oil in a lux?!! []

An equally good question would be: why would anyone put fully synthetic oil in an old S2? Older eight vlave cars are far more likely to run on 5w synthetic oil without issue, than S2s and 2.7s (which both share the same short engine). Generally though, it suits neither, although some run well enough.

 

[vitesse]

I've been using Chevron fully synthetic -5-40 sae for many years in the 924S & before that -Comma-ditto with positive results-around 1L per 2500 miles-much better than previously used semi-synth.These engines are meant to use some oil & do so when used enthusiastically-general punting around,ours is no worse than any car.
Now Costco have stopped selling the Chevron.I am considering using Mobil 1 as in the 964,as they still sell that.

 

[mr brightside]

Mine does away with 2l in 4k, i'm going to try 15w40 too.

 

[Copperman05]

Although tempted I'm not going to get started on the oil debate again. But as Oli points out the dip stick could also be providing different readings. To the OP are you sure you have taken dip-stick readings whilst the engine is warm on both occasions, I know that oil will generally run down into the sump once once it has stopped running for a while, perhaps this is affecting your dip stick readings.

Just a thought..

Edd

 

[Sandspider]

Copperman, I thought of everything and checked it all twice! (5 mins after engine stop, one hour after engine stop, next morning). My drive does slope slightly so I compared it with flat ground readings (the difference was negligible). I knew my oil was going, but it's only recently that I measured it carefully (noting down mileages and oil top ups in my little book) and realised how much was going!

Interestingly (!) enough, I popped into Halfords today to look at their oil selection. I knew what I was after, but the youth behind the counter wanted to use his computer so I let him look up recommended oils for a 1986 normally aspirated 944. His machine recommended either 5w40 fully synthetic, or 15w40 (or possibly 50, can't quite remember) mineral oil! (I didn't buy either, as the only 15w40 stuff they had wasn't suitable for injection engines - pretty sure mine has injectors!)

Giles

 

[944 man]

It doesnt matter what it says in the manual Edd. It wouldnt matter if it said it in all manuals. Empirical evidence; and experience of many, many owners/vehicles shows that 'thin' oils do not suit these engines. As I have already stated: 5w synthetic works well in my own old car, with little or no use at all, but MANY other vehicles, especially newer block-type 944s, suffer from massively increased oil consumption when using them. This is an unarguable fact.

 

[Copperman05]

ORIGINAL: 944 man

It doesnt matter what it says in the manual Edd.  It wouldnt matter if it said it in all manuals.  Empirical evidence; and experience of many, many owners/vehicles shows that 'thin' oils do not suit these engines.  As I have already stated: 5w synthetic works well in my own old car, with little or no use at all, but MANY other vehicles, especially newer block-type 944s, suffer from massively increased oil consumption when using them.  This is an unarguable fact.

I did'nt even say anything about manuals! You just cant resisit can you Simon![]


But seeing that you must get me started. I must admit that it does seem strange that as you are one who is often referring to how unsuitable these oils are for our engines and then tells everyone that you run your cars on the very same stuff! Shouldnt you be taking some of your own advice Simon and start getting that horrid, low viscosity, synthetic, engine killing muck out of your lovely sweet Porsche engines? Or perhaps you like an argument for arguments sake?

I'm still not convinced regarding low viscosity oil and their unsuitability, mine runs on 5W-40 fully synth and hasnt used a drop in over 2000 miles, fact, I also have not lost any oil pressure, infact I think I gained some, fact. Add the fact that my Porsche user manual (only now am I mentioning manuals[]) actually recommends 5w-40 oil, but your not interested in that, perhaps you know something they dont?

Granted 5W40 would probably not be a wise thing to put in my Dads 1964 Jag Mk2 but I really dont see the problem in using it in most modern fuel injected engines such as those in our cars.

The debate no doubt will go on...

Edd

 

[944 man]

Only one manual states 5w-. My 250's didnt and neither did the 968's, Im sure. This has been confirmed by Neil, whose manual also only lists 10w-. I have 5w- because it was given to me by a sponsor and it was 'installed' without my prior knowledge. I sometimes mention this to demonstrate that some engines fair better than others with it, although in reality it is usually later block engines that are badly affected (2,7 8v & 3.0 16v).

I was very carefull to point out that empirical evidence supported my claim. As Im sure that you know, empirical evidence is that observed...