My 1.6 diesel Octavia DGS estate is coming up 100K miles and has recently started frequently keeping the fan on after switching off the engine. I assumed this was about regen with the DPF system.  Most of my journeys are well over 50 miles (Anglesey - Chester - Manchester - Brighouse) and for short journeys of say less than 5 miles I use the bus. I became worried as I felt this should not be happening as often as it did.

 

I decided to investigate if there was a fuel additive which might help, and eventually added some Wynn's DPF cleaner to a full tank of diesel.  My usual response to such additives is that it is expensive and ineffective snake oil but after about 50 miles of continuous motorway driving, the fan over-run ceased, the idle revs dropped and the stop-start began to operate as it used to.

 

I am delighted and surprised.  Two tankfuls and a thousand miles later, all seems well.

 

Is this a coincidence? 

Edited 22 December, 20232 yr by BionicJohn

6 hours ago, BionicJohn said:

Is this a coincidence?

Dunno. I accept your personal account, but am surprised that a particulate cleaner made it through the combustion chamber in an effective form.

If it worked then great, but I am very wary of such additives.
Maybe it had been trying to do a regen which kept being interrupted by you stopping the car hence the fan running on more than normal. After adding the cleaner you took it on over 50 miles of motorway after which it was ok. Possibly the 50 miles of motorway was all it needed to complete a dpf regen and the cleaner being present was coincidental ?

Proper dpf cleaning is done by connecting into the exhaust before the dpf by removing a pipe, or sensor, then dpf cleaner added under pressure from an air line whilst the engine is running. 
I agree with Paws4Thot and would add that if a cleaning substance is resilient enough to make it through the combustion chamber then do you really want it inside the rest of the fuel system ?

Edited 23 December, 20232 yr by classic

55 minutes ago, classic said:

Maybe it had been trying to do a regen which kept being interrupted by you stopping the car hence the fan running on more than normal. After adding the cleaner you took it on over 50 miles of motorway after which it was ok. Possibly the 50 miles of motorway was all it needed to complete a dpf regen and the cleaner being present was coincidental ?

 

From what he has written that is the case, the regen finally was able to complete.

 

However far from leaving him in a joyous situation it leaves the worrying question of why a regen took so many motorway miles, the ideal conditions, to initiate and complete.

 

From being aware of a regen initiating or the one time the dashboard said that I had to drive the vehicle to initiate one it has never taken more than 4 or 5 miles under the right conditions to complete.

 

The dashboard warning was when I was doing the write off repairs, lots of start ups and moving in and out of garage etc with no driving. That regen would have had more soot to burn than a scheduled one yet still completed between junctions 10 and 11 of the M23, - 7.5kms, I would say it had completed within 5km, maybe add a couple of kms getting there but I doubt the conditions were right till the motorway.

Perhaps I should clarify further. Most of my journeys are 50 miles plus - the vast proportion without stopping at 60mph or more. Regen was rare, then became every time the engine was switched off.  The stop-start rarely kicked in.

 

After adding the Wynn's, it took another 300 miles or so before the post switch off regen didn't occur and stop-start worked.

 

I hadn't changed my driving pattern significantly so it's hard to tell if the car sorted itself out or the Wynn's was effective.

 

I too have doubts similar to those described above.  OTOH, Wynn's 28263 gets very positive reviews on Amazon and Halfords/Feefo.

 

Either way, the car's running better.

Edited 23 December, 20232 yr by BionicJohn

Are the dpf systems of the type with an additional injector in the exhaust? That may well make use of the additive. Otherwise I'm with the majority and you are experiencing a placebo affect. I'm a big believer in placebos. But not with mechanical stuff. 

My best (benefit of the doubt) guess is the additive alters the exhaust temp and that helps the regen complete.

8 minutes ago, MarkyG82 said:

My best (benefit of the doubt) guess is the additive alters the exhaust temp and that helps the regen complete.

That's a distinct possibility.

11 minutes ago, MarkyG82 said:

Are the dpf systems of the type with an additional injector in the exhaust

Nope

wynn's making excellent stuff.

Used their off-car dpf flushing liquid when my dpf got completely clogged and removed in the garage.

Used their on-car dpf cleaner spray with great results. The dpf continues to clog until egr will be replaced (egr cooler was replaced already) but looks like the egr is the culprit here.