Hi All,

I just wondered if anyone has done sufficient mileage in a CR diesel engine and had to have the DPF replaced when it was checked (beyond the 100k mark, as indicated in the service schedule), but through wear and tear, rather than a specific fault or failure?

What I'm trying to get at is - what's the shelf-life for a DPF from new? Do they really need replacing after so many miles, or is there someone here (for example) with 300k on the clock and still on the original DPF?

Cheers,

H

PS: Not sure if this should be in the Octavia forum, or a general forum, so mods can move if necessary.

The DPF will have a finite life before it becomes clogged with ash. Not all the particles caught in the filter are carbon, all oil products contain minute traces of metal and silicon compounds.

From a quick google it appears that the spec (BS EN 950) for ash content in diesel is max 0.01% by weight, I have found analysis results indicating a typical of 0.001%.

Over 100,000 miles at 50mpg you will use around 7,000kg of diesel. At 0.001% ash that will leave 70 grams of unburnable deposit in the DPF. Is that enough to block it? At the max ash content there will be 700 grams of unburnable ash in the DPF

Maybe this is a reason to use premium diesels that, being semi-synthetic, will have lower ash content.

Take a look at this fascinating document (well as a chemist, it is to me )

http://www.chevron.com/products/prodserv/fuels/documents/Diesel_Fuel_Tech_Review.pdf

The DPF will have a finite life before it becomes clogged with ash. Not all the particles caught in the filter are carbon, all oil products contain minute traces of metal and silicon compounds.

From a quick google it appears that the spec (BS EN 950) for ash content in diesel is max 0.01% by weight, I have found analysis results indicating a typical of 0.001%.

Over 100,000 miles at 50mpg you will use around 7,000kg of diesel. At 0.001% ash that will leave 70 grams of unburnable deposit in the DPF. Is that enough to block it? At the max ash content there will be 700 grams of unburnable ash in the DPF

Maybe this is a reason to use premium diesels that, being semi-synthetic, will have lower ash content.

Take a look at this fascinating document (well as a chemist, it is to me )

http://www.chevron.com/products/prodserv/fuels/documents/Diesel_Fuel_Tech_Review.pdf

Very interesting - quite revealing in certain areas - like DPF regens being performed by injecting extra diesel fuel later in the engine cycle so that unburnt fuel from the engine burns instead in the exhaust/DPF in order to burn off any excess ash . Does this mean that some DPF cars which are driven predominately on short runs , will emit more pollution/emissions than the emission level that they were tested/assigned to by the manufacturer ? We know that DPF regens also adversly affects the fuel economy . At a £1000 a go for a new DPF it does make you wonder whether buying a modern Diesel was the right thing to do !?

Edited 10 October, 201114 yr by vwcabriolet1971

Very interesting - quite revealing in certain areas - like DPF regens being performed by injecting extra diesel fuel later in the engine cycle so that unburnt fuel from the engine burns instead in the exhaust/DPF in order to burn off any excess ash . Does this mean that some DPF cars which are driven predominately on short runs , will emit more pollution/emissions than the emission level that they were tested/assigned to by the manufacturer ? We know that DPF regens also adversly affects the fuel economy . At a £1000 a go for a new DPF it does make you wonder whether buying a modern Diesel was the right thing to do !?

The extra shot of diesel going into the exhaust also means you cant run bio diesel more than 5%. A small amount of that diesel will go down the bores & mix with the engine oil. As Bio is not mineral based it wont mix with engine oil & over time will break down the engine oil reducing its effectivenes

A DPF reduces mpg, the Mk1 superb had one fitted on later models & it dropped mpg by about 20%

We were told on the Superb to expect to change the DPF after 80,000 miles. A nice little bill that would be

There is also now talk that the particles emitted after the DPF has dealt with the soot are so fine that the lungs cant filter them & they can go into the blood stream, now if thats true in a few years instead of a few people with lung issues there will be loads with nasty little particles floating through all their organs & the brain causing God knows what problems "diesel cancer ??"

DPF's More proof of ill thought through Eurocrats legislation

What about if you simply take the thing off and refit if necessary prior to the MOT test? Would that affect performance positively, and get around the problem?

What about if you simply take the thing off and refit if necessary prior to the MOT test? Would that affect performance positively, and get around the problem?

If only it were that simple

The car has to be remapped to run without it & then would need to be mapped back when you refit, & again when you take it off. A heck of alot of work. At present cars with the DPF removed will pass the MOT test but Im not convinced that will always be the case. as of next jan I believe the car has to pass a visual inspection that its fitted so the only way of getting round that is to knock the inside out of a very expensive DPF & remap the car.

Many current cars are older engine designs adapted to run with a DPF. As experience with the DPF increases and as engines designed from scratch to run with a dPF hit the market the situation may hopefully improve.

I think also as more start to fail cheaper replacements will become available. catolithic converters were a small fortune when they first came out but pattern ones are now a lot cheaper