Hello,

I would like to ask for your help. I have two different engine. DFGA and CXXB. 2.0 liter with adblue and 1.6 liter without adblue. The oil ash mass quantity is:

• DFGA - 60g

• CXXB - 11g

The ash mass limit is 80g.

Both cars have the same mileage and are used in the same way. Why is there such a big difference between the two numbers? Is 60g a lot? How effective is DPF cleaning? I'm not talking about regeneration.

Thank you!

Edited Saturday at 18:224 days by fdani

Which engine has the lower ash count - the 2.0 litre Adblu one?

I'd think 60g is fairly high, but I guess it depends on how long it will take to add the remaining 20g.

Does the DFGA engine use/burn more oil than the CXXB?

1 minute ago, Warrior193 said:

Which engine has the lower ash count - the 2.0 litre Adblu one?

I'd think 60g is fairly high, but I guess it depends on how long it will take to add the remaining 20g.

Hello,

The 1.6-litre engine has a lower ash content.

2 minutes ago, Breezy_Pete said:

Does the DFGA engine use/burn more oil than the CXXB?

The cxxb doesn’t use up the oil; as for the dfga, I’m not sure. I haven’t used the dfga much yet.

Edited Saturday at 19:584 days by fdani

I predict that you will find that the DFGA needs topping up with oil between services.

DPF ash load primarily depends on mileage and the number of regens. While it is possible that on EU6 engines it is measured / derived from DPF pressure loss after regen (doubt it), at least on our 2012 Roomster's EU5 1.6TDI CAYC 105bhp engine the ash load is simply calculated and increased based on mileage and number of regens, no measurements involved. If you experience frequent regens, you will find ash load going up quickly even though there is no change in pressure readings around DPF, i.e. no actual ash.

4 hours ago, dieselV6 said:

DPF ash load primarily depends on mileage and the number of regens. While it is possible that on EU6 engines it is measured / derived from DPF pressure loss after regen (doubt it), at least on our 2012 Roomster's EU5 1.6TDI CAYC 105bhp engine the ash load is simply calculated and increased based on mileage and number of regens, no measurements involved. If you experience frequent regens, you will find ash load going up quickly even though there is no change in pressure readings around DPF, i.e. no actual ash.

Could this 60g be a natural occurrence? The worst-case scenario is that oil gets into the DPF. If the 60 g is a value calculated from the regenerations, it could not have accumulated from the normal regeneration cycles. It is currently regenerating every 350 km.

Not sure what the exact calc for ash loading is, but it involves both number of regens and mileage. What's the mileage on each car/engine? In any case, if there are no signs of restriction in the exhaust (power loss, increased fuel consumption, regen completion issues etc.), the large amount of "accumulated ash mass" is just imaginary, there is far less ash in the DPF in reality. It is just a number / counter in the ECU which by the way can be adapted to a smaller value with VCDS, at least on earlier engines like CAYC. I honestly think that ash number was just put there to cover backside in case of clogged DPFs over the car's life, and also to force replacing DPFs latest at a certain mileage / after certain number of regens or both. The correct way to evaluate amount of ash would be to measure and average pressure loss after completion of each regen and indicate that DPF pressure loss post regen is getting on the high side, but my guess is that given varying temperatures and gas flow, the exhaust sensors used for it are either not accurate or not reliable enough, especially after many years of use / high mileage.

Edited Sunday at 07:574 days by dieselV6

13 minutes ago, dieselV6 said:

Not sure what the exact calc for ash loading is, but it involves both number of regens and mileage. What's the mileage on each car/engine? In any case, if there are no signs of restriction in the exhaust (power loss, increased fuel consumption, regen completion issues etc.), the large amount of "accumulated ash" is just imaginary, there is far less ash in reality, it is just a number in the ECU which by the way can be adapted to a smaller value with VCDS, at least on earlier engines like CAYC. I honestly think that ash number was just put there to cover backside in case of clogged DPFs over the car's life, and also to force replacing DPFs at most at a certain mileage. The correct way to evaluate amount of ash would be to measure and average pressure loss after completion of each regen, but my guess is that given varying temperatures and gas flow, the exhaust sensors used for it are either not accurate or not reliable enough, especially after many years of use / high mileage.

I managed to obtain data from two 2.0-litre engines. 181000km - 55g and 130000km - 47g. The CXXB is now the main suspect.

Again, you might be chasing ghosts, at least on CAYC one will for sure end up with ash mass measurement exceeding limit after enough mileage and regens even if the DPF is empty of ash altogether, it is just a calculation in the ECU that does not take into account DPF pressure measurements at all.

Or in other words, if you make a 300 regens and drive 100k km, the calc could be e.g. num regens x 0.1g + num kkm * 0.3g (I pulled numbers out of thin air, just like the calc in your car's ECU) resulting in 60g ash mass "measurement" even if in reality there would be only 15g-20g ash in the DPF at that point. Conversely, if you use poor quality, ash generating oil or if the engine burns a lot of oil, you may find clogged DPF while the ECU's "ash mass measurement" shows 20g or less, as in fact quite a few people have experienced.

May I ask why you are chasing after this number? Are there any other issues with the engine to even be looking at ash mass?

Just to chime in, my car 2014 Vrs 2.0 Tdi CUPA engine, manual gearbox, has 248kkm now and OBD11 shows oil ash mass 57g with the limit being also 80g.

My car uses about 1,5dl of oil per 1000km, has been like this for the last 100kkm. Only used 5W30 oil.

The engine has good power and i can get 5-5,3 liters/100km consumption with 225/40/18 tyres in the summer with speeds of 100-120kmh.

4 hours ago, dieselV6 said:

Again, you might be chasing ghosts, at least on CAYC one will for sure end up with ash mass measurement exceeding limit after enough mileage and regens even if the DPF is empty of ash altogether, it is just a calculation in the ECU that does not take into account DPF pressure measurements at all.

Or in other words, if you make a 300 regens and drive 100k km, the calc could be e.g. num regens x 0.1g + num kkm * 0.3g (I pulled numbers out of thin air, just like the calc in your car's ECU) resulting in 60g ash mass "measurement" even if in reality there would be only 15g-20g ash in the DPF at that point. Conversely, if you use poor quality, ash generating oil or if the engine burns a lot of oil, you may find clogged DPF while the ECU's "ash mass measurement" shows 20g or less, as in fact quite a few people have experienced.

May I ask why you are chasing after this number? Are there any other issues with the engine to even be looking at ash mass?

This is the quickest way I can access this data using VCDS. In theory, it should reflect the actual condition, but I’m not entirely sure whether I’m correct.

This is exactly what I am trying to say, the "accumulated ash mass" is just VW's / ECU's theory. In practice, actual DPF condition is OK until clogged enough to cause backpressure and related loss of performance and problems with completing regen or frequent regens. Can be well before 80g, can also be way after 80g. I stress that this is certainly the case for EU5 engines, perhaps EU6 ones have better pressure monitoring, but I doubt it. The only way to be sure would be to swap the DPF without resetting ECU, drive for a while and look at the accumulated ash mass reading sometime afterwards. On EU5 TDI, for sure the ECU would not notice new DPF and just keep increasing accumulated ash value in line with mileage / number of regens. I suspect it is the same for EU6 TDIs, but not 100% sure.

On 27/09/2026 at 17:01, dieselV6 said:

This is exactly what I am trying to say, the "accumulated ash mass" is just VW's / ECU's theory. In practice, actual DPF condition is OK until clogged enough to cause backpressure and related loss of performance and problems with completing regen or frequent regens. Can be well before 80g, can also be way after 80g. I stress that this is certainly the case for EU5 engines, perhaps EU6 ones have better pressure monitoring, but I doubt it. The only way to be sure would be to swap the DPF without resetting ECU, drive for a while and look at the accumulated ash mass reading sometime afterwards. On EU5 TDI, for sure the ECU would not notice new DPF and just keep increasing accumulated ash value in line with mileage / number of regens. I suspect it is the same for EU6 TDIs, but not 100% sure.

Okay, thank you. But if the calculated soot mass is over 80g limit, the ecu will can disabled or go to error. Regardless of the actual value.

Yes, but you can adapt the value to a smaller number. I had to in the Roomster (CAYC engine), as it came from factory with regen causing issues (and fuel in oil) that were only fixed after quite a few regens over a period of a year or so, and resulted in 15g "accumulated ash" that simply wasn't there. It is just a number that can be edited.

Edited 5 hours ago5 hr by dieselV6

51 minutes ago, dieselV6 said:

Yes, but you can adapt the value to a smaller number. I had to in the Roomster (CAYC engine), as it came from factory with regen causing issues (and fuel in oil) that were only fixed after quite a few regens over a period of a year or so, and resulted in 15g "accumulated ash" that simply wasn't there. It is just a number that can be edited.

Out of interest, if I would now edit the ash load value with OBD11 back to 0g with my original dpf with ash load value now showing 57g, what would happen?

Even if the dpf wasnt cleaned?

Is the engines ECU making more frequent dpf regens when the ash load value is closing the maximum of 80g?

Even if the dpf wasnt really that full at all? I would think that its a precaution to protect the engine and dpf.

I do not know, in fact logic suggests opposite, i.e. higher tolerance to DPF pressure loss at end of regen when ash value is high as the base pressure loss due to ash would be higher. All I know is that the ash value has very little to do with actual pressure loss across the DPF / level of clogging.

Perhaps, and I am only speculating, ECU could allow higher values of DPF pressure loss at end of regen when the ash value is high, as partly clogged DPF would have higher pressure loss than an empty one. Way to confirm this would be to take a car with low ash value that has trouble finishing regens, set its ash value to close to the limit and see if the regens improve. Never tried that. But most likely nothing / not much would happen until the DPF was actually clogged.

A more sinister (but sadly likely) interpretation would be that the accumulated ash value counter as it is implemented was mainly put there into ECU to ensure profits of DPF manufacturers and exhaust workshops from replacement DPFs... who knows.

In any case, if the ash value is over the limit yet your DPF is still fine, ash value can be adjusted down.

Edited 4 hours ago4 hr by dieselV6

There seems to be a huge disconnect between what car manufacturers say about Diesel Particulate Filters (DPFs) and what actual parts makers and service technicians recommend.

Car manufacturers often treat the DPF as a component that lasts until it completely clogs up, after which the official recommendation in the dealership is usually an expensive total replacement. However, automotive component manufacturers and repair professionals recommend preventive cleaning of particulate filters, particularly DPFs, between 150,000 and 200,000 miles.

The main focus here is the clearance of accumulated residual ash, which cannot be burned off during normal vehicle driving or standard regeneration (since active and passive regeneration only handle soot, not ash). Letting the ash accumulate until total failure puts extreme thermal stress on the ceramic core and raises backpressure, which can heavily strain your turbo and engine. Doing a professional cleaning at higher mileages helps prolong component life and avoids a costly full replacement.

While I have no issue with your statement, you may find that a lot of cars show "accumulated ash" value at or near the limit coded in the ECU far earlier, around 100000mile mark, which again points to ECU signalling an imaginary problem using an imaginary ash value in order to either trade in the car or pay for a new DPF halfway through its life... just my opinion.

32 minutes ago, dieselV6 said:

While I have no issue with your statement, you may find that a lot of cars show "accumulated ash" value at or near the limit coded in the ECU far earlier, around 100000mile mark, which again points to ECU signalling an imaginary problem using an imaginary ash value in order to either trade in the car or pay for a new DPF halfway through its life... just my opinion.

Manufacturer of part, not car, recommends machine cleaning on 150000 miles, resetting ASH volume. you can do it or no. like lifetime oil in gearbox and other ****.

Interesting, with my car i have done some "preventive" maintenance and it would seem that dpf cleaning is one thing to consider also.

As I said earlier i have now almost 250kkm or 155t miles on the dash and the dpf is original and never been cleaned before.

I dont have any symptoms yet with dpf clogging but maybe im asking when would i need to do that job? When the regens happen more frequently and there is a dpf warning light on the dash, maybe?

I have now and then checked with obd11 the distance last travelled before a regen has occured and i would say its in between 250-400km depending of my everyday driving trips. Is this normal distance between regens?

In the Octavia 3 its a big job to get the dpf out of the engine bay, you have to drop the subframe, thank god i dont have all-wheel drive, even more job involved.