Audi 2.0L TFSI Oil Consumption...

[Joe90_guy]

I stumbled upon this video which was posted on YouTube a few weeks ago...

https://www.youtube.com/watch?v=vlSlPVoY-wE

It's a Dutch TV report about the problems owners of Audis, fitted with the 2.0L TFSI petrol engine, have had with excessive oil consumption. Now I'm well aware that this is an old problem and that Audi have stepped up to the plate to fix these cars.

However I was really interested in the part of the video where someone empties a box of 'problem pistons' onto a bench! Wow! That's definitely what I would call a dirty piston! Part of me finds it hard to comprehend how pistons could get that bad when Audi Europe insists that drivers only use some of the best specified full synthetic oils that money can buy. The other thing this video confirms is that these dirty pistons suffer from stuck oil control rings.

I have long thought that the fundamental oil loss problem with these engines is a two-step process.

The first step happens when some clever-clever engineer crosses a bridge he should never cross and says 'it is normal for all engines to consume oil'. What I think this means is the engineer has compromised the ring pack to minimise ring friction in order to maximise fuel economy and power output. This obviously increases blow-by but the engineer relies on a well designed, but 'physical' oil separator to stop too much oil being routed back to the intake and burnt. However the oil separator will not knock out any oil that's truly in the vapour phase and this is what I believe can happen if you dump too much fuel in oil. When this unexpected oil hits the cold inlet system you get inlet valve fouling but this is the least of your problems. The real problem is that the oil burns (or more likely partially burns) and starts dumping deposits in the cylinder. These deposits progressively move down the side of the piston. Yes they foul the top and second grooves but the first and second rings constantly splay and retract as pressure changes. They also constantly rotate. This means they tend not to stick. It's when these deposits start to accumulate in the oil control ring that things truly go to pot. The ring tends to stick flush in its groove and you lose oil control. Once this happens you have oil rushing up through the second and first ring gaps directly into the cylinder and that's when oil consumption goes massively out of control.

Interesting stuff...

PS - sorry the video is in Flemish. Don't bother with YouTube's Auto-translate option as you just get gibberish (eg the ring is constipated!).

 

[wemay]

Motor Oil, no matter how stout, is never the cure for a bad design or poorly executed good design.

 

[userfriendly]

Belgian TV dumkoff. One set of pistons is from an air cooled gasoline engine and the other from a Diesel engine. Neither set is from the Audi shown and the problem is not the fault of the engine oil, but the injection or tune up.

 

[Joe90_guy]

Oh dear....

First off, at the start of the clip, you will see the NPO logo in the corner of the screen. NPO stands for Nederlandse Publieke Omroep or Dutch Public Broadcasting. Belgium is a different country.

Secondly, 'dumkoff' is a German word and is usually spelt as 'Dummkopf' (or stupid head which is rather ironic under the circumstances).

Third, yes, the Dutch (not Belgian or German) expert picks up an air cooled cylinder to give a simple lesson on how piston rings distribute oil on the liner. I am sure, for reasons of accuracy, he would have preferred to pick up an Audi 2.0L TFSI engine block but they aren't quite so easy to hold in one hand.

Fourthly, the piston shown at 2.46 in the video (the one with the stuck ring) is indeed an Audi TFSI piston. It has the tell tale gap in the land supporting the oil control ring.

Finally, your comments about this being the fault of the injectors and state of tune are interesting. Sadly they don't quite stack up with the fact that Audi is fixing this problem by replacing the pistons, rings and rods on the affected engines.


Thank you for your interest in this thread...

 

[zeng]

I would hypothesize that, during the top to bottom movement of the pistons (intake/firing strokes), the oil scraper ring (second from top) fails to scrape and prevent the oil on the surface of the liners from below i.e oil control ring (third from top) from passing by top compression ring (top ring) . It allows engine oil to enter into the combustion chamber during top to bottom movement of pistons (intake/firing strokes).

Initial varnish develops inside the combustion chamber from the 'bypassed' engine oils and increases in severity, leading to sludge formation on piston top, then moving to top ring groove, then second (scraper) ring groove, then the third (oil control ) ring groove, then into piston skirt and then into lower half of engine.

JMO.

 

[Joe90_guy]

Yes. That's it exactly Zeng.

One of the other things I note from this video footage is that whilst everyone is aware of the significant differences between mineral and full synthetic motor oils, when it comes to what they look like after you've set fire to them, they look remarkably and horribly similar!

 

[Nebroch]

Volkswagen AG is constantly in trouble, with almost all of their products. It makes me wonder what will happen to Germany's economic miracle..

 

[KrisZ]

Could it have something to do with Europe's insistence on super long OCI to the tune of 30k kilometers (18.5 k miles)?
Nah, cannot be, synthetics simply do not sludge, varnish or cake up rings. Those things are reserved for conventional oils. And since Europe uses mostly synthetics, this can only lead us to the only logical conclusion that it was a bad design

 

[Joe90_guy]

If it can be fixed by redesigning and replacing the pistons, rings and con rods, then sadly yes, it's a design fault.

I do have some sympathy for VAG. I suspect they did huge amounts of trashy, bop-til-you-drop engine testing to assure themselves that all was well. I suspect they just caught out by the vagaries of vapour pressure which sadly no-one in the lubricant industry seems to be remotely aware of.

 

[BrocLuno]

Low tension ring paks to help with fuel economy... Replacements are likely standard tension paks, to make sure they scrape successfully ...

Likely they are Mahle... They have become popular with racers over here and are often sold by custom/race engine builders. If you're going to go that way, long change intervals are not in the offing ...

I would never do what they are doing with long change intervals with the range of temps in northern Europe? Come on, change it at 5K (miles) and keep your engine happy

 

[SwampSurvivor]

And ring problem isn't going to be cured by heavy oil ...

 

[chrisri]

Originally Posted By: Nebroch
Volkswagen AG is constantly in trouble, with almost all of their products. It makes me wonder what will happen to Germany's economic miracle..

VW before 1974 and introduction of brilliant mk1 Golf didn't build anything other than POS Beetle, and its derivatives. It didn't built anything interesting after IMO. Pedantic build doesn't necessarily mean well engineered vehicle.

 

[BrocLuno]

It's a gas engine so you have access to the top of the cylinder through the plug hole. If I bought one of these used, I'd be very likely to lay a heavy shot of Break-Free gun solvent into each cylinder and let it sit overnight. Run some MMO in the crankcase (mix) and see if I could free the rings...

If so, then I'd switch to Rotella T6 (syn) for the higher rates of detergency and see if I could keep the rings free... Low tension rings will work, but they have to kept free. Once they stick, you're in trouble ...

 

[Joe90_guy]

I have often pondered on whether Audi's well publicised problems could have been avoided by using a less volatile oil. It's almost certain that once you have a stuck oil control ring then it doesn't much matter what oil you use; thick, thin, mineral or synthetic, the oil will be still forced into the combustion chamber.

However I tend to think that if Audi had, from new, used an oil will a very low volatility, and particularly one with a heavy front end, then extractive distillation of the oil in the presence of re-evaporating fuel in the sump could have been minimised and less oil would have ended up being burnt. I guess we will just never know...

 

[wemay]

Originally Posted By: Joe90_guy
I have often pondered on whether Audi's well publicised problems could have been avoided by using a less volatile oil. It's almost certain that once you have a stuck oil control ring then it doesn't much matter what oil you use; thick, thin, mineral or synthetic, the oil will be still forced into the combustion chamber.

However I tend to think that if Audi had, from new, used an oil will a very low volatility, and particularly one with a heavy front end, then extractive distillation of the oil in the presence of re-evaporating fuel in the sump could have been minimised and less oil would have ended up being burnt. I guess we will just never know...


Wouldn't this just stretch the miles-to-occurrence out further? But not necessarily solve the problem either? I guess it depends how far out.

 

[Joe90_guy]

Oil volatility on the TFSI engine is a bit like smoking cigarettes. You know if you're on sixty a day, then it's very likely you're going pop off prematurely. Cutting down is definitely a good thing but doesn't completely eliminate the risk. I guess mathematically you only need to cut down enough such that there's an equal risk something else will get you instead!

This is my say of saying I think the answer is 4% Noack!

 

[SR5]

Originally Posted By: Joe90_guy

One of the other things I note from this video footage is that whilst everyone is aware of the significant differences between mineral and full synthetic motor oils, when it comes to what they look like after you've set fire to them, they look remarkably and horribly similar!


Yes, I noticed that too.
This may be a silly question, but would a mineral oil have left less deposits?
I ask because rotary engines, burn a little oil by design, and so they only run mineral oils (not synthetics or blends) because they burn easier and cleaner.

Still a bad design. But I wonder if a heavy mineral oil (like 15w40 or shock! the old 20W-50) changed regularly (like every 10k KM or 6k mi) would have fared better. Ignoring the cold start issues that northern Europe would have.

just think out loud….

 

[Joe90_guy]

That's a very good question. My gut feel is that because raw minerals are worse in terms of oxidation stability, they might burn faster and cleaner in that hot, pressurised, oxygen rich chemical reactor we call the combustion chamber.

And yes, when I first started picking up on the TFSI problem, my instant reaction was to tell people to use 20W50 in order to minimise the oil's volatility. I found out however that Audi owners can be a funny bunch. All the ones I spoke to were very reluctant to move away from the Audi's uber-expensive recommended oil, even though the life if this oil could be measured in days and in extreme instances, just a few hours!

 

[chrisri]

It's hard to move away from OEM recommendations when it's for a very expensive piece of equipment, even if it doesn't make sense.