So where does all the oil go?

[tweenster]

OK, this is not meant to be a serious oil usage thread, but a light hearted discussion.

 

As I was driving this morning a thought occurred to me; if some engines are using a lot of oil, where does it go? Usually, oil burning is evident by blue smoke out of the exhaust but as far as I am aware, no high oil users seem to exhibit this trait. So where does it go? How is it 'used up'? 

[lordsummit]

This is troubling me. There's no smoke from mine, but it's devoured oil at a vast rate of knots. I'd love to know.

[Defenderben]

Depends

A classic, is worn valve stems - this allows a small amount of oil past the valve into the cylinder when left and gives a quick puff of smoke on start up. Lots of people never notice it as it quickly goes, but slowly consumes oil.

Other is as mentioned see blue smoke - common is worn piston rings, a quick compression test can find that one.

Even small amounts can be burnt off without plumes of smoke, so can often go unnoticed. Best time is at night look in your mirrors when the car behinds headlights shows up your "invisible smoke trial".

Then the others such as a leak and leaking into coolant.

Edited 20 July, 2014 by Defenderben

[James I]

Our Fabia used oil, never smoked so to speak but always had very black sticky soot allover the tailpipes and onto the boot lid.

 

 The only time smoke was evident was after we did how fast at Bedford, we went to the pub for lunch, the Fabia following me said the car was smoking, but that was the only time.

 

 Three years old and MOT time. emissions were very low so I guess no major oil problem.

 

 My belief is that oil mist moves through the breather system and straight into the inlet manifold where the vapour gets burnt up in the combustion process.

[xman]

 

 My belief is that oil mist moves through the breather system and straight into the inlet manifold where the vapour gets burnt up in the combustion process.

 

I'll second that.

 

All engines produce a great deal of oil mist in the crankcase, simply because a lot of oil is flung around by the crank or squirted back to the sump by the oil control rings etc.

 

Its the job of the oil separator to recover the oil in the crackcase airspace and its part of the crankcase ventilation system. VAG have used a variety of oil separator designs over the years, some have been very poor designs and prone to getting clogged. 

 

I have suggested in another thread that the vrs woes may be down to faulty oil separators, but no-one commented. I cited my experience of a mk1 htp engine where I have experienced  an occasion where the seperator oil return valve appeared to be stuck closed and only opened after an oil change when I heard the accumulated oil drain suddenly back.( sounded like liquid being emptied from a bottle at height) Prior to that event, the engine had experienced a mysterious loss of over 1 litre of oil over a few hundred miles when in the previous 120k miles it had used none. Since then, it has returned to normal, using no oil.

 

Although the 1.2 htp separator design has a return valve, the 1.2 tsi used on the mk2 is a totally different design,using a plastic multiple passage device that works on a vortex principle ( think dyson). No return valve and much simpler, but I suspect will only work well if the oil is kept clean. The micro vortex design looks as if it could well become blocked easily with sludge or carbon.

 

I suggest someone go look at the seperator design on vrs engines and look for possible fail modes e.g. a stuck return valve.

Edited 20 July, 2014 by xman

[lol-lol]

Burns I suppose.  A very light oil so burns clean.

 

Now Mazda RX8s and Kawasaki H1s, Suzuki kettles etc that is burning oil, litre per 1000 miles rather than per 5000 miles. 

[tweenster]

Depends

A classic, is worn valve stems - this allows a small amount of oil past the valve into the cylinder when left and gives a quick puff of smoke on start up. Lots of people never notice it as it quickly goes, but slowly consumes oil.

Other is as mentioned see blue smoke - common is worn piston rings, a quick compression test can find that one.

Even small amounts can be burnt off without plumes of smoke, so can often go unnoticed. Best time is at night look in your mirrors when the car behinds headlights shows up your "invisible smoke trial".

Then the others such as a leak and leaking into coolant.

That is the classic method usually in high mileage engines but I wouldn't have thought a new vRS would suffer like that.

 

 My belief is that oil mist moves through the breather system and straight into the inlet manifold where the vapour gets burnt up in the combustion process.

Interesting ...

 

I'll second that.

 

All engines produce a great deal of oil mist in the crankcase, simply because a lot of oil is flung around by the crank or squirted back to the sump by the oil control rings etc.

And more interesting. But surely oil mist is well known about and how to deal with it? Oh silly me ...

 

Burns I suppose.  A very light oil so burns clean.

 

Now Mazda RX8s and Kawasaki H1s, Suzuki kettles etc that is burning oil, litre per 1000 miles rather than per 5000 miles. 

Ah, Mazda RX8s; making Fabia vRS oil usage look positively minimal. And those rotor tips don't come cheap either!

 

Some interesting theories that I am nowhere near qualified enough to comment on!

[Defenderben]

^^^Hammer the hell out of your stone cold engine and you can give it similar wear of an engine with very high mileage.

I thought you were asking a general oil usage question, I did not realise it was specific to low mileage, well cared for and duly warmed up engines, before thrashing them

Edited 20 July, 2014 by Defenderben

[James I]

I did notice our car would use oil when doing the daily drive, low revs and stop start traffic. I took it on a track day and it used no oil at all! Bouncing off the red line all day and no oil used at all.

 

Whatever the reason is as to why a twin charger uses so much oil is probably going to pondered over for years to come. I bet VAG know what the reason is and how to resolve the issue but if they publicise this then they will have a massive recall and an even bigger bill to rectify it.

[xman]

 I bet VAG know what the reason is and how to resolve the issue but if they publicise this then they will have a massive recall and an even bigger bill to rectify it.

 

Yes, they probably do know the real cause.

 

Further to my earlier post, the oil separator is an integral item built into the engine on most designs today and so cannot be changed. Could the earlier attempt to address the oil burning issue by modify the external breather be the hint that the real reason lies in the oil separator? The only way to modify that is to redesign the engine......that's why VAG are keeping schtum...

Edited 20 July, 2014 by xman

[R4zb3rry]

Most of mine does get shoved out the exhaust as a blue cloud, mostly after it's done a few miles at NSL and then come to roundabout/junction and give it some beans.

Always let it warm up to at least 80c before even consider pushing it on so, I presume it must the type of journeys it does that highlight it's penchant for oil use.

[Jabozuma]

CTHE revision to twincharger engine had different part number piston rings and some valve train modification as well. There was something in oil transportation system as well, cannot remeber now. Valve stems with too much tolerance will use very small amounts of oil in NA motors due to vacuum in the intake but not so much or othing in charged engine sincw positive pressure keeps the oil "in" in intake valves.

Crank case ventilation system allowing for pressure build up can push oil back into combustion chamber especially when it is a very low viscosity oil (5w30). My theory is that this combined with crap tolerances in open deck grey iron casting of the cylinders allow liners to deform outside the ability of rings to compensate, so high crank case pressure pushes the oil into combustikn chamber and through the exhaust. This is something they are not able to correct without changing tooling in Chemnitz so they simply phase that engine out.

[tweenster]

Some interesting stuff coming out here; thanks.

[GeneralPurpose]

Well followed a Vrs along the A12. He was doing 70mph most of the time and as he came off the throttle and back on again there was often a small puff of blue smoke which as the following car I could see, just! I doubt the driver would ever be aware of it even at night in the interior mirror if being followed by another car with his headlights on, as the puff was very very small. I think that is the key here. Most Vrs's that are using oil do so gradually and it's just unnoticed.

[Jabozuma]

I think though combustion chamber is the only way out really so no surprises there. I do see, especially winter months, smoke in other peoples headlights behind me when I boot it. The question is, how does it get to the combustion chamber. I do not think however the oil gets burned in the turbo i.e. leaky seals.

[GeneralPurpose]

I'm same as you Jabo, I'm certain it's mostly lost through combustion. I've had one of these motors apart for other reasons at my nephews garage and the oil control rings seemed more worn that I would have imagined on an engine that had covered just 14k miles. I replaced them as he said it was using some small amount of oil. This particular engine was in a Gold GTI and it regularly got thrashed, but even so I would not have expected the wear that I saw. He was quite happy with it afterwards and zero oil use he says. Time will tell.

[Ootohere]

A small point about CAVE 1.4 TSI 180 ps engines 2009-2012 end of production before the Revised CTHE with lower co2 grams km,

last quarter 2012,

then 2013- 2014 as in the Facelift Seat Ibiza Cupra and the revised published Emissions & MPG, top speed etc.

 

CAVE engines that use next to no oil, maybe the odd top up between annual or 10,000 mile services, can produce soot, and blow it out the exhaust in a cloud after trundling around, or just running at below about 2,400 rpm and opening it up.

Or puffs as it gets full on turbo,

& they can have little puffs or big puffs of soot out the rear day in and out and still not use oil & be totally sound engines,

many still, 3 - 4 years on.

 

Different Engine parts & Map on a CTHE (& internal pressures) from the CAVE,

DSG changes differently and Torque is at different RPM,

& to generalise, they run a bit more economically and with a bit more BHP as standard when on 98-99 ron,

& possible run a bit better when on 95 ron than a CAVE does.

(Just an opinion obviously.)

 

george

Edited 21 July, 2014 by goneoffSKi

[Jabozuma]

Everything wears out but oil control rings are usually not the ones to go really, unless piston are not running straight/has a wobble - there was something I read about piston skirts design being not optimal in some way, some oscillation was mentioned - could lead to oil control rings being loaded and wearing off? They are after all rather soft, not like compression rings.

That would suggest that the oil gets into cylinder from down below, not the valve train, which as I wrote above is less likely a scenario in charged motor. However, twinchargers run in NA mode at low loads and I was seeing vacuum readouts from MAP most of the time during normal commuting. 

 

Did you have a chance to do low viscosity fluid cylinder/piston leakage test? I am asking in hope of understanding whether that open deck webless cylinder design and crap manufacturing tolerances lead to distorted cylinder linings?

[Jabozuma]

A small point about CAVE 1.4 TSI 180 ps engines 2009-2012 end of production before the Revised CTHE with lower co2 grams km,

last quarter 2012,

then 2013- 2014 as in the Facelift Seat Ibiza Cupra and the revised published Emissions & MPG, top speed etc.

 

CAVE engines that use next to no oil, maybe the odd top up between annual or 10,000 mile services, can produce soot, and blow it out the exhaust in a cloud after trundling around, or just running at below about 2,400 rpm and opening it up.

Or puffs as it gets full on turbo,

& they can have little puffs or big puffs of soot out the rear day in and out and still not use oil & be totally sound engines,

many still, 3 - 4 years on.

 

Different Engine parts & Map on a CTHE (& internal pressures) from the CAVE,

DSG changes differently and Torque is at different RPM,

& to generalise, they run a bit more economically and with a bit more BHP as standard when on 98-99 ron,

& possible run a bit better when on 95 ron than a CAVE does.

(Just an opinion obviously.)

 

george

 

When I was doing lowering springs at Skoda Main Dealer I asked about updated map for my car he said there wasn't any...

[Ootohere]

Was he referring to no ECU Update for a CTHE ?

That sounds correct.

 

It will be an ECU out of the Car and back to the Factory then if locked to Dealership Technicians if there are early 

CTHE like the early few built that have had Oil usage & required replacing.

(no breather mod or ECU update suggestions from Dealers if a CTHE is using oil, or running rough on start up if all other 

things are correct and in good order.)

Edited 21 July, 2014 by goneoffSKi

[GeneralPurpose]

Jabo, not a leak down test but did a compression test and it was 100% within spec. Can't remember what the actual figs were now but all cylinders were even and right up at the top of the range. All cross hatching in place no glazing just this strange wear to the oil control rings. This as you say points to possible piston flutter at high revs. It is usual to redesign pistons with a thicker top ring to allow higher revs without flutter and also gives better heat distribution. I bet that would cure it. Longer term I wonder if this probably flutter is part of what is giving the engines problems. But I would have thought that VW would know just about all there is to know about this. I know it and I only really design bike engines, which sometimes get used in cars! 

 

goneoffski, brilliant information as usual. Glad your on here. 

[Jabozuma]

I think the problem they have is that they are chasing economy and emissions so lower reciprocating mass at a cost of compromised piston design would fit the bill. Mind you, forged pistons can be almost skirtless as we know so...

Wouldn't crank resonance frequency tuning eliminate piston flutter as well?

On a face value this is so bizarre this day and age that quite hard to explain without knowing all the facts and having stripped few oil guzzlers next to few perfect engines for comparison.

 

I remember reading about first days of F1 turbo charged engines. I think it was Leyland who was developing it (might be wrong) and they could not understand why engines were seizing all the time. They were faaaar more clever than any of us:)

 It turned out, after they picked up the leftovers and measured everything in detail, that at high boost the torque produced by the engine was simply twisting the block into a pretzel (almost ) and pistons were seizing. They increased corss-sections and were able to run sick boost levels 

 

Not suggesting this is the case here at all but one has to be humble and question everything, however strange it might be .

[Jabozuma]

Correction, crank resonance tuning (choosing alloy and cross-section size) will have no effect on piston flutter. What has an effect is cranck case ventilation system managing pressure surges.

[lordsummit]

So maybe that's why they do the breather mod?

[Ootohere]

No maybe about it !

Engines from 2009- 2012 were failing in growing numbers.

That is why the do the Breather Pipe & Valve Modification (Update) and an ECU Engine Management Update.

 

That was to alter the Engines internal Pressures.

& for a while it works, but for at least one member here, it appears to have worked for lots of miles.

 

It resolved nothing really on almost all the already failing engines, others were good and have never had the Breather Pipe Modification or valve mod,

But Volkswagen revised the Engine, they had to because of the failure rate,

they fitted new Stronger and longer lasting components that could take the wear,

revised the Engine Management, fitted as standard the CTHE Breather System.

 

Apart from some of the earliest Revised and Released CTHE engines it seem to have worked.

 

george