I must say that our car only uses between the max and min level marks on the dipstick between 18,600 mile services.

Quite impressed with that, since my 1 litre VW 507 spec Shell Optima bottle of oil should last the life of the car.

It really depends on driving style. For fleet use a figure of about 80k was mentioned. With shortish runs I would expect much less.

My colleague who got rid of his dpf equipped Fabia was told by Skoda that a min of 20miles commute was needed.

The way the dpf works is it collects soot which is burnt off to form ash which has a smaller particle size, this is trapped in the PDF and eventually it will fill up and need to be replaced. I have seen some company's offering dpf cleaning, I'm not sure hoe effective this is.

Mark

My Scout has 83.5k now and no sign of the DPF needing to be replaced.

When the dpf does an active regeneration the sequence injects extra diesel to initiate a catalytic reaction to increases the exhaust temperature so that the soot can be burned off. A bit of The extra diesel ends up in the sump hence rising oil levels.

Right - that makes sense

Thanks

Mark999, where are you getting all this ash from? Diesel fuel doesn't burn to ash, it burns to CO2, H2O and a few related compounds. If it didn't you'll see ash coming out the back of every vehicle. To form ash in a DPF you need to have burn contaminants, high sulphur fuel was an old source, oil additives are another. If you have an oil consumption problem, it will likely cause DPF problems.

I haven't seen the rash of 80k mile DPF failures yet. My scout is on 80,000km, I'll let you know but I'm not expecting any. Despite it's previous owners doing largely city running. There are two audis in my family with DPF sensor replacements. DPF's themselves are fine.

So far it's a lot of scaremongering and no hard data.

BTW, if you have fuel in your sump, it's completely unrelated to DPF burn. Fuel into the sump is a leak somewhere in your fuel system. Even a cold diesel cranking will put diesel out the exhaust rather than past the rings. At operating temps there is no show of hosing diesel out of the combustion bowl, across the piston and down the sides of the bore.

http://pmmonline.co.uk/technical/diesel-particulate-filters-explained

Some more interesting reading

http://www.stocksy.co.uk/articles/Cars/diesel_particulate_filters_dpfs_and_rising_oil_levels_the_uk_government_demonstrates_the_law_of_unintended_consequences/

Had to have the DPF sensor changed on my '09 Octavia CR 170 (luckily just before the warranty ran out!). Seems like it might be the sensor rather than the actual filter that's a weak link? Called RAC out on Skoda's advice when the warning light came on and the guy said those sensors are delicate little things.

I had a sensor changed on an Audi, then no further issue, car did well over 100k in three years, I now have the Yeti and it has done 58k in 15 months and not an issue either.

I read further up this thread about Mazda's euro 6 engine and CO2 emission quote, is this not irrelevant as the DPF removes diesel particles as the name suggests, I will also add that the DPF used by VAG is a much better system than the French car manufacturers use, I had a relative with a 307 HDi and it died with only 50k on the clock the bill was close to £2,000 to repair.

Mark999, there is nothing about ash in either of the articles you linked.

The second article refers to a claim the author made previously about fuel trickling past the rings during the exhaust stroke (impossible with cylinder temps during regen conditions) causing rising fuel levels. He then uses that as the cause of a volvo and a fiat having diesel engine runaway.

Neither article backs your claims. The fuel sump loading cannot happen like that as cylinder temps and exhaust temps are far higher than diesel auto-ignition temps during regen. I'd be looking for leaks in the fuel systems of those vehicles.

http://en.wikipedia.org/wiki/Diesel_particulate_filter

Hope this clears up the ash issue

Mark

Oil in the Fuel / Fuel in Oil is usually a sign of tandem pump failure.

Edited 3 November, 201213 yr by petetdi

Rubbish. The majority of noise comes from the minority of owners. My car has no current problems.

Ah, you've had no problems with your DPF so the concept of the DPF being unreliable is rubbish.

I'm not the original owner but there is nothing in the service history about DPF problems.

And why would there be, the DPF isn't a serviceable item.

BTW, if you have fuel in your sump, it's completely unrelated to DPF burn.

Wrong.

I just didn't consider this thread worth the effort.

So far it's a lot of scaremongering and no hard data.

:think:

Mark999, no the wiki article doesn't clear up anything. It's a general blurb which attempts to cover all types ever used.

Silver, the DPF is no more or less reliable than any other vehicle part. Like turbochargers.

Some engines have known issues, some usages are also known to cause issues.

OctyOGG came out with the blanket statement that all DPF's are unreliable. Which certainly isn't the case.

Mark999 has claimed all DPF's will fill up with ash and need replaced by about 80,000 miles. Which again isn't the case and can't be backed up.

If a car had a DPF replacement, it would be noted in the service history.

Please explain this mechanism for getting fuel into the oil during a regen.

Information fro a VAG engineer. http://uk-mkivs.net/forums/t/343695.aspx

Quote: The prime reason for a DPF is to reduce particulate matter entering the atmosphere. Particulate matter is found in the form of soot, which is produced during diesel combustion. The DPF traps most of the soot which would normally travel down the exhaust and into the atmosphere. The DPF can hold a certain amount of soot, but not a huge quantity and therefore it needs to go through a process called ‘regeneration’ in order to clear the soot loading. When the soot goes through a ‘regeneration’ process it will be converted to a much smaller amount of ash. The ash is non-removable.

Note answers to question

Question: How does regeneration affect the oil life?

Answer: On each regeneration or attempted regeneration, a certain diesel fuel amount is injected into the engine oil which reduces the oil life. If the "INSP" light in the instrument cluster comes on, the engine oil is exhausted and must be changed. Failure to do so could damage the engine.

I did not claim that all DPFs will need replacement by 80k. The life of a PDF is dependant upon many factors the most important being driving conditions and driving style. A design life of 80k is typical for passenger vehicles. Under ideal conditions it may well last much longer.

The DPF is a filter all filters will eventually block and need replacement. I would have no problem with this if the replacement cost was reasonable, unfortunately it isn't.

Over 60.000 km with my 1.6 cr and apart from the regen no issues with the dpf. Though I must admit that I will be looking for a tsi next year (waiting for the new Octavia III, of course). EGR and dpf cause a lot of problems certainly after 100.000 km, I am told. The cr will go before that mileage. It's a good engine, nevertheless, with an average of 51 mpg.

(still can't quote)

Firstly. VAG technical support specialist =/= VAG Engineer.

Mark999, you're missing the vital part in the soot/ash thing. Soot that is made up of carbon doesn't burn to ash. It burns off cleanly to mainly CO2 which leaves no ash. The only compounds which form ash are impurities and pollutants, which as I wrote earlier, come from such things as additives in the oil.

A DPF is closer in function to a catalytic converter than the vacuum cleaner bag which most assume they are. How often do you replace the catalytic converters in petrol cars?

The answer given on oil dilution is *******s. Fuel is never injected into engine oil. Perhaps something was missed in the transposing of answers to that website.

I'm currently looking at a VW 'Service Training, Self-Study Programme 336' document titled "The catalytic coated diesel particulate filter" and it references the exact same quote as mentioned by mark999:

The prime reason for a DPF is to reduce particulate matter entering the atmosphere. Particulate matter is found in the form of soot, which is produced during diesel combustion. The DPF traps most of the soot which would normally travel down the exhaust and into the atmosphere. The DPF can hold a certain amount of soot, but not a huge quantity and therefore it needs to go through a process called ‘regeneration’ in order to clear the soot loading. When the soot goes through a ‘regeneration’ process it will be converted to a much smaller amount of ash. The ash is non-removable.

I've also read about the issue of rising oil levels as a direct result of diesel fuel contamination during normal DPF operation in a VAG training document but annoyingly can't find it.

Basic chemistry says that ash is heavy oxides. Compounds that aren't gaseous and stick around when something has been burnt. Some Examples being magnesium oxide, aluminium oxide etc.

Soot is pretty much all carbon. The oxide (ash) of carbon is CO2 which is a gas and not a solid. It's pretty hard to plug anything with CO2.

Wear particles, oil additives, fuel pollutants etc can form ash which would eventually plug a DPF. Obviously the more issues your engine has, the more of these it sends out the exhaust. But there's no way a healthy engine and appropriate driving style would lead to DPF plug up and replacement in 80,000 miles. I don't believe 80,000 miles is the average car design life either. Outside the UK that's still a young car that hasn't reached halfway.

120k on the clock from new and no probs. it came on once when the wife and I swapped cars for about 3 months to balance out the mileage across 2 cars. Ran it to work on the normal 40 minute A road drive and it regenerated fine.

I think people under normal circumstances have issues if they do very few miles or drive likability an old fart:-)

103,000 miles only seen the DPF light once a week after i picked car up but went out after 10 minuets.

120k on the clock from new and no probs. it came on once when the wife and I swapped cars for about 3 months to balance out the mileage across 2 cars. Ran it to work on the normal 40 minute A road drive and it regenerated fine.

I think people under normal circumstances have issues if they do very few miles or drive likability an old fart:-)

at work we call it the fuel saver syndrome.

15 months in only 7K on the clock and I've not had a light on yet. I've had a number of active regens with the usual increses in tickover but that's it so looks like the ECU and DPF are coping well with my driving patterns.

I did 44k miles in my FL vRS CR including 5 miles each way to work 5 days a week where in winter the coolant doesn't even reach 90C.  Didn't see the DPF light once.

60 plate FL vRS CR, has done 47k ish and never had a problem with DPF from new. That includes a fair few cold morning journeys of less than a mile for school runs and nipping up to tescos!

Soot is pretty much all carbon. The oxide (ash) of carbon is CO2 which is a gas and not a solid. It's pretty hard to plug anything with CO2.

 

See post #66, Volkswagen say it turns to ash and is stored inside the DPF. It is this level of ash that determines the life of the DPF. This isn't me, it's the VAG engineering team!

 

It might be 80,000 miles on one car and 180,000 miles on another car, the soot burnt depends on the soot produced which is dependent on the way in which the car is driven so the life of a DPF can be hugely variable.

See post #67. Carbon burns to CO2 gas. Only impurities create ash.