Hello All!

I have a 2016 Mk 3 Superb with CRLB engine and 358k on the clock. Very few issues over it's lifetime and oil change every 10k. Mostly motorway driving at 70 and runs really well.

I've been searching round this forum but can't really find anything that covers the problem.

The fuel consumption dropped from around 60 mpg to below 45 mpg over a couple of months, together with DPF warning coming up at irregular intervals. Engine light came on and diagnostics found a damaged Exhaust Pressure Sensor. Replaced it and consumption is slowing improving.

I'm fairly sure the DPF is the root of the problem so the next thing to try is a forced regen with a fuel additive. The one I'm planning to use is Archoil AR6400-D Max.

I appreciate I could have it specialist cleaned, but recently a few people report they get just as good results using a fuel additive.

Are there any recommendations for a better additive?

Edited 14 January14 Jan by Paulws1953
Spelling mistake

I’d always avoid additives as not needed here usually, but saying that your car has done crazy miles

BTW diesels do lower MPG in winter, so keep that in mind too

Archoil 6400 is pretty good additive for clearing the accumulated soot from the DPF, especially when the regens were interrupted many times and/or the car was driven mainly for short journeys. BUT this is not your case.

Most likely, your DPF has accumulated ash not soot because it reached its end of life, looking at the miles you’ve driven the car.

Could also be a pressure sensor reporting incorrect values.

Thank you for the reply. 6400 has made a difference, but not much. End of life sounds plausible. As far as I can see, the only way forward is a specialist diagnosis. However, there are dozens of diagnostic "specialists" around. The process involves a thorough understanding and ability to correctly interpret results, and I wonder how many "specialists" are all that special.

I agree with @fr1nklyn s diagnosis.

With 350k km on the clock it's quite normal that the DPF could be full with ash rather than soot and a regen or additives won't be able to fix this.

There are places you can have the DPF removed and cleaned of ash but I've never owned a car long enough to have this done so have no opinion if it's cost effective

@Paulws1953 I see there is this garage with good Google reviews around your place https://essextuningltd.co.uk/dpf-cleaning-bury-st-edmunds/ I don't know are they really good, but you can give them a call and ask for diagnostics(not for cleaning directly).

They need to reset the DPF values after cleaning if they do the cleaning and then force regen to allow the system adapt to the new pressure sensor values.

Some DPFs are totally blocked or damaged, and you cannot clean them, from what I know. In this case you can search for second hand part, e.g. on eBay, but you will need the part number of yours.

Thank you. A good lead!