DPF Ash Oil level

[pinkpanther]

Following dramatically increased active regeneration frequency post EA189 emission update I purchased the VAG DPF android app, so I could keep a closer eye of the DPF.

 

I'm not massively knowledgeable regarding the DPF, but assume the soot load progressively increases the resistance across the DPF and, once it reaches a critical point, the ECU triggers an active regeneration. These active regenerations (evidenced higher tickover / heat / cooling fans running on after switch off) tended to occur every 200-300 miles prior to the EA189 emission update, but started to occur every 60-90 miles, immediately following the update,

 

I subsequently had the car stage 1 mapped by Shark and the frequency of active regeneration has returned to pre-EA189 levels (every 200-300 miles).

 

The VAG DPF app tells me the "Oil Ash" level is currently 34%. I assume the DPF converts Soot to Ash and once the Oil Ash level reaches 100% the filter has reached the end of it's lifespan?

 

The VAG DPF app told me the Oil Ash level was 29% at 53k miles and is now 34% at 58k miles. On this basis the VAG DPF app is showing an increase of 5% in Oil Ash, over the last 5K miles.

 

Given only 2 data points (thus far) I'm unsure if DPF ash will continue to rise in a linear fashion, but assuming it does can I expect to see the DPF last well beyond 100K miles? 

 

Based on current observations 99% Oil Ash level will equate to 123K miles. 

 

Additionally I recently realised the car won't actively regenerate if the fuel light is on. I checked the VAG DPF app and saw the DPF was 93% clogged. I assumed a planned motorway journey would allow it to actively regenerate, but returned home to find it reading 100% +11%. The dasboard light didn't illuminate at any point, The fuel light typically comes on when the car has a predicted range of 65 miles. It does however still have around 1 gallon remaining, when the range is 0, so I generally wait until this point before refueling.

 

Edited 23 September, 2017 by pinkpanther

[weasley]

Most of what you said is correct.  The oil ash thing isn’t quite right though.  Soot is the product of burning fuel; it is small particles of mostly carbon-based materials and is what makes the smoke from a diesel engine.  The DPF’s job is to trap it so it doesn’t go into the atmosphere for us to breathe, as it is carcinogenic.

 

The problem is that the engine also burns small amounts of the engine oil as it runs.  The engine oil is made of predominantly base oil’s (hydrocarbons) with some additives added.  The additives are things such as detergents, dispersants, antiwear, friction modifiers and so on and each type is a different type of chemical.  The detergents are organometallic soaps, meaning they are molecules with carbon, hydrogen but also metal elements in them, such as calcium and magnesium.  The antiwear additive is ZDDP, or zinc dialkydithiophosphate, which clearly contains zinc (another metal).  When these additives burn, the metals get oxidised and become their oxides, which form powdery ash-type material.

 

During regeneration the DPF is overheated and the carbon-based soot is burnt away, thus clearing the DPF.  However the metal oxide ash does not burn and stays in the DPF.  It therefore accumulates over time and will eventually permanently block the DPF.  This is why you must use low-ash forming oils in diesels with DPFs (for us it is oils with the 507 00 specification).

 

Hence the ECU tracks both soot loading and ash loading (which is essentially how much is left in the DPF after a regen).

Edited 23 September, 2017 by weasley

[Urrell]

We have in Lincoln a VAG Specialist that advises a DPF Cleaning Service at 80k for £239.

https://www.lvsag.co.uk/pricing/

[pinkpanther]

28 minutes ago, weasley said:

Most of what you said is correct.  The oil ash thing isn’t quite right though.  Soot is the product of burning fuel; it is small particles of mostly carbon-based materials and is what makes the smoke from a diesel engine.  The DPF’s job is to trap it so it doesn’t go into the atmosphere for us to breathe, as it is carcinogenic.

 

The problem is that the engine also burns small amounts of the engine oil as it runs.  The engine oil is made of predominantly base oil’s (hydrocarbons) with some additives added.  The additives are things such as detergents, dispersants, antiwear, friction modifiers and so on and each type is a different type of chemical.  The detergents are organometallic soaps, meaning they are molecules with carbon, hydrogen but also metal elements in them, such as calcium and magnesium.  The antiwear additive is ZDDP, or zinc dialkydithiophosphate, which clearly contains zinc (another metal).  When these additives burn, the metals get oxidised and become their oxides, which form powdery ash-type material.

 

During regeneration the DPF is overheated and the carbon-based soot is burnt away, thus clearing the DPF.  However the metal oxide ash does not burn and stays in the DPF.  It therefore accumulates over time and will eventually permanently block the DPF.  This is why you must use low-ash forming oils in diesels with DPFs (for us it is oils with the 507 00 specification).

 

Hence the ECU tracks both soot loading and ash loading (which is essentially how much is left in the DPF after a regen).

Many thanks for this weasley

Edited 23 September, 2017 by pinkpanther

[pinkpanther]

18 minutes ago, Urrell said:

We have in Lincoln a VAG Specialist that advises a DPF Cleaning Service at 80k for £239.

https://www.lvsag.co.uk/pricing/

Many thanks Urrell - I'll bear this in mind, although am hopeful I'll see well in excess of 80K miles on my original DPF.

 

I used a similar independent (http://www.autohausdolby.co.uk/) for the most recent service on my Yeti. Given it's now out of warranty I enquired what was required / recommended at the 3 year service. Local main dealer quoted >£400 for long-life service, brake fluid change and Haldex fluid change. The independent quoted £275 (£149 for a major service - oil / oil filter / air filter / fuel filter / pollen filter + £59 for brake fluid change + £67 for Haldex fluid flush / change). They seemed very knowledgeable, so I opted for the independent and a 32% saving

[Brijo]

3 hours ago, weasley said:

.... zinc dialkydithiophosphate ....

Nice. 

 

Seriously, that post was masterly.  I take my hat off to you

[weasley]

5 minutes ago, Brijo said:

Nice. 

 

Seriously, that post was masterly.  I take my hat off to you

Thanks!  After 25 years working with the stuff, you pick up a thing or two.  Also my job includes training people about how oil works.  I’m glad it’s helping.

[SuperbTWM]

So what you saying is the long term ownership of your car has got considerably more expensive due to the update?

 

Will be interesting to see what the ash loading is in the future but by those figures the DPF would of lasted a hell of a lot longer without the emissions update.