I wonder if I could draw upon the group's collective wisdom on this one?

Last week I got the "bing" of death and a message about removing some oil popped up along with a yellow oil can and exclamation mark.

As an oil change was scheduled for the day after, I didn't really worry about it other than to do a quick Google which suggested that the cause was a failed DPF regen dumping about 200ml of diesel into the oil. 😳

Sure enough, oil and filter change fixed the issue. Or so it seemed. Three days later, pottering up motorway, put foot down, bing of death and associated illuminations.

So, further research reveals that the internet is roughly evenly split amongst four solutions:

A - Do nothing and ignore it.

B - Drain/ Syphon 200ml or so of oil / diesel off.

C - Go for a half hour low gear, high revs thrash (easier said than done with a DSG)

D - Proceed straight to workshop for oil and filter change. Do not pass Go, do not collect £200.

Obviously only the last option addresses the level and contamination issues, but an oil change every week is going to work out expensive.

So, what is the collective wisdom?

Is 200ml of diesel in, what, 5 litres(?) of oil a big issue? Does the system recognise the failure and stop retrying or will it just keep dumping fuel into the sump?

Have I just been unlucky or do I need to start investigating the reasons why DPF regen is failing?

Has anyone else been this way before and how did they solve it?

Any advice / experience gratefully received.

I’m sure others will chime in with specific diesel experience but if the car is older and high mileage you could have leaking injectors or high pressure fuel pump putting diesel into the oil. Not good.

Good, if unpleasant thought. 3yo/ 75k, so on the lower end of my list of possibilities, but deffo worth considering.

Quick thoughts.

3 hours ago, Deadwood said:

Go for a half hour low gear, high revs thrash (easier said than done with a DSG)

Half an hour wouldn't be enough if the DPF really needed a blow out, and it's lower gear higher revs rather rev the nuts off you want the heat but this might not be a good idea if the car's dumping fuel into the oil and you don't know why.

Can you borrow a scan tool to check the short term and long term fuel trims.

What's the history of this 3 year old 75k-mile car, how many engine oil changes and any other servicing and maintenance work done or repairs or problems.

Have you searched the forum for similar issue(s) on your particular engine.

Have you checked for Recalls.

Were there any comments about fuel in the oil that came out of the engine, was the triangle of doom and message mentioned t whoever done the oil change.

I'm sure others than me will have better information and advice to give.

Good luck.

Edited 26 January26 Jan by nta16
fat finger typing

Thanks, all. Spoke with dealer service dept, and I'm not sure whether the mystery is solved but this is what they said...

Yes, a failed regen will dump fuel (about 200ml by inference) into the oil, but this doesn't matter as it gets burned off later. (Not too convinced about that, unless it's something like the oil/fuel gets hot, fuel evaporates first and fumes are scavenged for reuse. 🤷)

Also the oil level rises after a successful regen as well! (Not sure why, though. What's entering the system? Can't be burned fuel... )

Anyway, the dealer workaround, they say, is to fill the oil 200-250ml shy of the full mark to allow for the regen process without triggering the overfill warning. 🫣

The other question is if the oil level rises after a successful regen, why isn't oil spraying out of the filler like a fountain? 🤔

If the oil is too diluted by Derv / Diesel which is also Oil that is not a good thing. (How VW Group used to cheat the NEDC in Audi, VW. Seat diesels...Dilute the engine oil.) You will see soon enough that the Diesel in the Oil will not Burn off. Change the OIl & filter IMO.

Oil sits high on the stick when hot/warm, a regen probably gets everything warmer but I don't know how far back (er, forward) but that's the thing these regens will take a good while if previous regens have failed to complete successfully.

For a good number of years diesels are sold to or bought by people who may not use them in a way must suitable to the most efficient running of the car, you may or may not be one of these people.

I've not heard of this fill 200ml below to allow for failed regen but when my wife had our one and only diesel these DPF weren't on it and it was an over complicated VW brand car.

Doing regens on the road can b e hard at times as you can't meet the requirements need, you can do a forced (or wotever its called) regen with a scan tool but you don't want to be parked on dry grass apparently things do get very hot.

You need to get the regen done then make sure you get regular successful regens after.

Despite diesel being so dirty some bits of it do need to be reasonable clean engine oil being one and I favour at least occasional use of the city? cleaner (😁) diesel fuel like Shell V-Power certainly two tankfuls before, during, after a service and/or MoT. The engine air filter being so clean doesn't matter apparently but it also doesn't want to like like a coal miner's handkerchief.

I think I might get the regen done successfully then change engine oil and filter (well get shot of the car really) but I could well be wrong.

Good luck let us know how you get on.

6 hours ago, Deadwood said:

Thanks, all. Spoke with dealer service dept, and I'm not sure whether the mystery is solved but this is what they said...

Yes, a failed regen will dump fuel (about 200ml by inference) into the oil, but this doesn't matter as it gets burned off later. (Not too convinced about that, unless it's something like the oil/fuel gets hot, fuel evaporates first and fumes are scavenged for reuse. 🤷)

Also the oil level rises after a successful regen as well! (Not sure why, though. What's entering the system? Can't be burned fuel... )

Anyway, the dealer workaround, they say, is to fill the oil 200-250ml shy of the full mark to allow for the regen process without triggering the overfill warning. 🫣

The other question is if the oil level rises after a successful regen, why isn't oil spraying out of the filler like a fountain? 🤔

The diesel in the oil will evaporate but obviously is less volatile than petrol so it will need a good long drive (45mins or so) where the engine oil ideally gets to the 100°C or so. As I’m sure you know diesel engines like to work and are slow to warm up for various reasons including their heavier construction and the fact there is no throttle plate etc.. so many short trips are going to increase the amount of fuel in the oil that is naturally washed down from bore by the rings and blow by.

28 minutes ago, whippersnapper said:

The diesel in the oil will evaporate but obviously is less volatile than petrol so it will need a good long drive (45mins or so) where the engine oil ideally gets to the 100°C or so. As I’m sure you know diesel engines like to work and are slow to warm up for various reasons including their heavier construction and the fact there is no throttle plate etc.. so many short trips are going to increase the amount of fuel in the oil that is naturally washed down from bore by the rings and blow by.

This appears to be key. The contamination is unavoidable, and appears to be deemed "within tolerances" for successful regens. Repeated failed regens cause the problem. Having done >300km in a Pug which used the same regen system, I'm more relaxed.

Now, the manual Pug encouraged shall we say, "spirited" driving. The Octa with DSG, winter, short trips doesn't, really. Still very quick off the mark, but still less , well, spirited.

Anyway, I'll post a more logical summary if my research shortly!

Thanks to everyone for their input.

54 minutes ago, nta16 said:

Oil sits high on the stick when hot/warm, a regen probably gets everything warmer but I don't know how far back (er, forward) but that's the thing these regens will take a good while if previous regens have failed to complete successfully.

For a good number of years diesels are sold to or bought by people who may not use them in a way must suitable to the most efficient running of the car, you may or may not be one of these people.

I've not heard of this fill 200ml below to allow for failed regen but when my wife had our one and only diesel these DPF weren't on it and it was an over complicated VW brand car.

Doing regens on the road can b e hard at times as you can't meet the requirements need, you can do a forced (or wotever its called) regen with a scan tool but you don't want to be parked on dry grass apparently things do get very hot.

You need to get the regen done then make sure you get regular successful regens after.

Despite diesel being so dirty some bits of it do need to be reasonable clean engine oil being one and I favour at least occasional use of the city? cleaner (😁) diesel fuel like Shell V-Power certainly two tankfuls before, during, after a service and/or MoT. The engine air filter being so clean doesn't matter apparently but it also doesn't want to like like a coal miner's handkerchief.

I think I might get the regen done successfully then change engine oil and filter (well get shot of the car really) but I could well be wrong.

Good luck let us know how you get on.

Good points, all of them. I have been a high mileage motorway driver for years and wanted to stick with 2.0l diesel simply from comfort zone. The wife's 1400 Fiesta terrifies me!

Anyway, I found out many things this afternoon, I'll post a summary in case it helps anyone else.

The dipstick was at max - not over. So we've dropped about 300-400ml (it's a litre from max to min) and we'll see how we go.

I take your point about just getting shut, but we'll see. My other car is an MG 🤣

@Deadwood Are your oil level checks at Normal Operating temperature, so an Indicated 90*oC or so & after a few minutes stopped on the flat after the engine is turned off? As the oil level should be checked. Then when stone cold the level can be compared.

6 minutes ago, Evolution13 said:

@Deadwood Are your oil level checks at Normal Operating temperature, so an Indicated 90*oC or so & after a few minutes stopped on the flat after the engine is turned off? As the oil level should be checked. Then when stone cold the level can be compared.

All at normal ops or within a few moments of stopping. Flat ground. Not done cold comps.

5 minutes ago, Deadwood said:

My other car is an MG 🤣

Until 3 years ago my one and only car for the previous 16 years was a 1973 MG Midget (outdated and basic even in 1973) and for 30+ ears I used various "classic" (over priced, over valued) old cars for daily use throughout the whole year, commutes (300 and 500 miles a week for periods), for work, UK & European holidays and weekends away, club and show events.

Now I bet you put your MG is a modern one 😄 (if not good odds on Tartan red B with chrome wire wheels, possibly BGT). 😁

Be interesting to see your case summary, though I might not understand all. 🙃

Good point about 'hot' and cold dipstick readings, with my wife's 2016 Fabia I can't remember any noticeable difference with the Midget unless I was going to drive it hard on holiday I'd only fill to about 80% of min to max, surprisingly it used very little oil and to be fair so far neither has the 9 year old Fabia, I like to be fair to VW when I can.

15 minutes ago, nta16 said:

Until 3 years ago my one and only car for the previous 16 years was a 1973 MG Midget (outdated and basic even in 1973) and for 30+ ears I used various "classic" (over priced, over valued) old cars for daily use throughout the whole year, commutes (300 and 500 miles a week for periods), for work, UK & European holidays and weekends away, club and show events.

Now I bet you put your MG is a modern one 😄 (if not good odds on Tartan red B with chrome wire wheels, possibly BGT). 😁

Be interesting to see your case summary, though I might not understand all. 🙃

Good point about 'hot' and cold dipstick readings, with my wife's 2016 Fabia I can't remember any noticeable difference with the Midget unless I was going to drive it hard on holiday I'd only fill to about 80% of min to max, surprisingly it used very little oil and to be fair so far neither has the 9 year old Fabia, I like to be fair to VW when I can.

🤣 Would love Tartan or Damask chrome, but I am beholden to a slightly scruffy, but mechanically good '78 GT. She did Toulouse in '24, broke my hip last year, so need to start warming her up again!

So 8/10 for Sherlock Skills!

I think she might have instilled the idea you might need to persist beyond a warning light... Whether that's a good position to take in this day and age is debatable! 🤣

You have room for a hip in the Bs. 😄 Scruffy don't matter it's how it goes (and should be going (used) and driven (as designed to be driven. In the Midget I promised not to overtake a single B, I'd always overtake them in pairs, not difficult and necessary with most B drivers. 😁 I can't remember having any leaks in the Bs but my memory isn't the best.

Done a tour or two up or near there but never been to that pub which suggests it didn't have well served real ale there or it was shut when we were near.

MG TwatNav -

1 hour ago, nta16 said:

You have room for a hip in the Bs. 😄 Scruffy don't matter it's how it goes (and should be going (used) and driven (as designed to be driven. In the Midget I promised not to overtake a single B, I'd always overtake them in pairs, not difficult and necessary with most B drivers. 😁 I can't remember having any leaks in the Bs but my memory isn't the best.

Done a tour or two up or near there but never been to that pub which suggests it didn't have well served real ale there or it was shut when we were near.

MG TwatNav -

Midgets were always too tight for me! But yeah, the rest can fit in a B. She's tight as a drum. The Bounty had seen better years, stopped there about three years ago round Christmas as we couldn't get in at Whitewell. Great breakfast!

No longer open. Great shame, it was a great place in the day. Decent food and decent beer.

At the risk of getting moaned at again for thread drift (again) you do have to be like my good self for a Spridget, slim, athletic and young.

Thinking about it now I don't think we were ever in the area in a MG though there were a few in the group (multi-marque club). I can remember on one of the tour there was a note on the route in Bowland that said at a particular point if you looked to the left you'd see the coast or Blackpool or something, it of course wasn't a clear day. that tour or another we were supposed to have a short tour or talk and lunch at the the nuclear place but it got cancelled, I don't think that was my fault.

Our tour organiser was part of the Wigton Motor Club and managed to get our little bumble on the same weekend as the RAC? National Rally stage in the area which normally isn't allowed but our paths were apart. Going along a nice single track road and I heard the sound of something mighty meaty and before I knew round the bend came a Group N? I froze taking up the whole road and without the slightest hesitation it went up the bank and by me before I knew almost blowing my doors off with its exhaust noise. Fabulous. It was going off script between garage points I think so we put it down as a figment of my imagination, and my good luck. I think it must have been on Tesco 99. 😃

20 something year old cars in the 1990s, both used for work and pleasure, after, not before, I bought the BGT I discovered I liked drop tops. My wife drove the B on the day of the photo and when I said at first tea/pee stop she was dropping back a bit she said at one point she had to drop a gear as the car seemed sluggish, I had a quick look, felt the rear wheels and suggested she might not have fully released the handbrake, the B reportedly went better after this, cleared the drums a bit at least. 😄 (teal blue, Henlys, local garage ("British Racing") Green)

12 hours ago, nta16 said:

At the risk of getting moaned at again for thread drift (again) you do have to be like my good self for a Spridget, slim, athletic and young.magination, and my good luck. I think it must have been on Tesco 99. 😃

🤣Yes, well, back to the case in hand!

So, after a bit of reading, it looks as if the situation is a bit like this:

Basically, fuel in the oil is an inevitable fact of life for anyone driving a car with a diesel engine, a DPF and a "post-injection" system for regenerating the DPF. The "post-injection" bit basically means pumping fuel into the cyclinder during late-phase power or exhaust strokes to pump it down the exhaust to the DPF where it bursts into flames and cleans 'said DPF. Inevitably some of that fuel washes down the cylinder wall, past the piston rings and into the sump. Failed regens lose no more fuel than successful ones, by the look of it, but it's the re-tries that kill you - simply the number of re-tries. So, yes, the level in the sump will go up after every regen and much more obviously so after 10 or so failed regens in rapid succession!

So, does it get burnt off? Well I think we all know the answer to that; there is no active method of recovering the fuel and "burning it off". However, there is some support for the theory that if the oil/fuel mix gets hot enough (100°C or so) for long enough (guessing hours rather than minutes) on a long run, then the diesel being lighter than the lub oil will evaporate first, and the vapour will be syphoned off by crankcase breather/ recycler scavenger systems that might be fitted. What proportion of the fuel is removed via this process is open to debate.

Does it impair the oil? On a binary scale, certainly. On a more graduated scale, the quality of lub oil degrades with usage, so there must be some degree of degradation that can be tolerated without unduly damaging the engine. One would think. Particularly if allowing fuel to leak into it is a "design feature". So, yes it still impairs the oil, but hopefully within acceptable/ tolerable limits.

So what do we think happened to my car? Well, it was due an oil change, so was probably carrying a fair load of fuel in oil, which triggered the overfill warning just before the oil change. The oil was changed and topped up to the full mark. It being the depths of winter, short days, short, slow journeys, etc., a regen or two later, a finnicky sensor kicks off. There are no fault codes that would suggest a failed regen, and the amount of "overfill" visible on the dipstick is, well, invisible!

Armed with that background, absence of fault codes and the knowledge that the dealership I spoke to acknowledge the situation by filling to slightly shy of full, we've dropped 300ml of oil, and will keep a close eye on it. If the same warning comes back in short order, oil and filter change again (groan) and then we've got some more serious diagnostics to do.

Thanks to everyone for their thoughts and advice.

Edited 27 January27 Jan by Deadwood

And to follow up, quickly, what can you do to minimise the effects of this "feature"?

The two big things seem to be:

1) Recognise that a big diesel isn't designed for short, slow runs. It needs to stretch its legs. Give it a run occasionally, especially in winter when 2 minutes to the shop are all it usually does. Apparently you need to find a road where you can keep speed up to about 50+mph and revs over 2,000 for half an hour so so to allow a regen to work. In the UK this means a motorway run. 🙄 Esp with DSG.

2) Recognise when it is in regen. Apparently signs are tick over about 1,000rpm rather than 800, slightly rough running and Auto Stop/Start unavailable. Watch for these before you switch off at the end of a run. There is a school of thought that says if you get home and these factors apply, go for a brisk whizz round the block until tickover's back down to 800. Sounds like a faff to me.

Edited 27 January27 Jan by Deadwood

I volunteer for the coastguard and it’s amazing how hard it is to get the 13 litre inline 6 700hp Scanias to warm up just ticking over. Diesels love load and love to work.