Leaving tank more than 1/4 full

[Sunstoner]

Ok, so your in depth survey of your mates taxis, and inherent wisdom, is sufficient to outweigh the entire knowledge base and expertise of the global vehicle manufacturer.
While I hold out little hope for you, maybe others can be saved!

Not wanting to particularly join in (however it is a forum afterall)....but surely WG was saying that : (if I understand correctly @WelshGas ?!)

If you do regular short journeys, make sure theres at least 20L in the tank on a regular basis

If you do long journeys, there will be little or no issues whilst running a full tank down to the fuel light.

and if you regularly (mostly) run with less than 20L in the tank (thus hampering the regen) then youre a numpty.

Doesnt this align with what VW are saying ?

 

[Lightning]

Not wanting to particularly join in (however it is a forum afterall)....but surely WG was saying that : (if I understand correctly @WelshGas ?!)

If you do regular short journeys, make sure theres at least 20L in the tank on a regular basis

If you do long journeys, there will be little or no issues whilst running a full tank down to the fuel light.

and if you regularly (mostly) run with less than 20L in the tank (thus hampering the regen) then youre a numpty.

Doesnt this align with what VW are saying ?

No it doesn’t align with what VW are saying.

VW simply state you must keep your tank more than a 1/4 full.

There is nothing from VW which states it’s ok to go below 1/4 of a tank on long journeys.

There is nothing from VW saying you only need to keep the tank greater than 1/4 full if you are doing short journeys. This is all unfounded supposition.

 

[Borris]

I just cannot understand the degree of hair pulling, arm waving and comments regarding " Not fit for purpose" or being put off buying the vehicle

I have just purchased my second T6 so clearly I haven't been put off from buying them. I haven't been hair pulling either, principally because I don't have that much to pull and yes the T6 is fit for purpose otherwise I wouldn't have paid good money for them.

However the issue is really whether, in a vehicle costing this much and made by one of the worlds leading vehicle manufacturers with its huge R and D budget, is this sound design or a bodge up?
Since I don't know of another manufacturer that insists in keeping the tank at least 25% full to avoid dpf problems then I can only conclude that it's the latter. Add to that, the stipulation that you must never fill the adblue tank to the brim or it messes up the sensors and a picture starts to build of a system that requires further R and D. If as has been mentioned, the former issue is to do with the fuel heating up as it circulates on a low tank then cool it. Instead it would appear that it's cheaper for VW to wash their hands of the issue by giving everyone a disclaimer label costing a few cents each.

No doubt VW will have rectified both of these issues on the T6-1! Ha ha

 

[Legin]

My two penneth.
The WelshGas long journey let it run from max to min is just fine and will not affect regens , the reason is the DPF will passive regen rather than force regen (injection of fuel) because the pre conditions are in place .
Even if it requests a forced regen it will be fine because it will just wait for next tank fill and do rgen then. Bottom line no problem.
The VW design will be based on the expectation that the tank doesnt get persistent short fills. However they have come to realise that there are folk that do this and they are often the short journey brigade so doble whammy. Hence the need for VW to point this out.

The details of how the regen works are complicated and not least how it works is very different pre and post dieselgate fix. There are documents out there that explain it in detail but its heavy going - so Ligtning how do I know all this - by reading said documents. I have also had my 140 yeti rolled back to pre fix so been through the mill for real.
The main outcome of dieselgate was massively increased egr to reduce temperatures and therefore NOx but other downsides result due to inadequate heat generation for the increased coke burn required. Answer more forced regens.

 

[WelshGas]

No it doesn’t align with what VW are saying.

VW simply state you must keep your tank more than a 1/4 full.

There is nothing from VW which states it’s ok to go below 1/4 of a tank on long journeys.

There is nothing from VW saying you only need to keep the tank greater than 1/4 full if you are doing short journeys. This is all unfounded supposition.

Obviously you don't understand the meaning of the word " May " used by VW. Your interpretation is that running below 1/4 tank means it " Will " affect DPF regeneration, which is not the case in the real world if the tank is filled with a minimum 20L at the first opportunity.
No one quibbles with the fact that you need a minimum fuel level for the Parking Heater to function.
Or the fact that running with very low fuel levels increase the risk of picking up contaminated fuel from the bottom of the tank.
In summary, lots of short trips keep the tank above 1/4tank. If on a long trip and the fuel level drops below 1/4 then fill up at the next opportunity, especially if you want to use the Parking Heater, and to avoid the possibility of a DPF regeneration being prevented when required.

 

[Lightning]

My two penneth.
The WelshGas long journey let it run from max to min is just fine and will not affect regens , the reason is the DPF will passive regen rather than force regen (injection of fuel) because the pre conditions are in place .
Even if it requests a forced regen it will be fine because it will just wait for next tank fill and do rgen then. Bottom line no problem.
The VW design will be based on the expectation that the tank doesnt get persistent short fills. However they have come to realise that there are folk that do this and they are often the short journey brigade so doble whammy. Hence the need for VW to point this out.

The details of how the regen works are complicated and not least how it works is very different pre and post dieselgate fix. There are documents out there that explain it in detail but its heavy going - so Ligtning how do I know all this - by reading said documents. I have also had my 140 yeti rolled back to pre fix so been through the mill for real.
The main outcome of dieselgate was massively increased egr to reduce temperatures and therefore NOx but other downsides result due to inadequate heat generation for the increased coke burn required. Answer more forced regens.

Again this appears to be a third party view and is not shared by VW. These documents which are out there, do they relate to the current hardware and software standard present on the T6? How do you know?

VW could easily have issued an operating instruction to not exceed x miles at below 1/4 of a tank. They chose not to. Why not? Do you think they issued an instruction to not use 1/4 of the tank without thinking about the adverse ramifications?

VW design the system and the software and are best placed to define how it should be used. If you choose not to follow their very clear instructions the liability is yours, not theirs.

 

[WelshGas]

Again this appears to be a third party view and is not shared by VW. These documents which are out there, do they relate to the current hardware and software standard present on the T6? How do you know?

VW could easily have issued an operating instruction to not exceed x miles at below 1/4 of a tank. They chose not to. Why not? Do you think they issued an instruction to not use 1/4 of the tank without thinking about the adverse ramifications?

VW design the system and the software and are best placed to define how it should be used. If you choose not to follow their very clear instructions the liability is yours, not theirs.

Such clear instructions that they used the word " MAY" in their handout.

 

[Lightning]

Such clear instructions that they used the word " MAY" in their handout.

It seems clear to me. They do not need to be able to guarantee that you will get a problem, to issue operating instructions to ensure you won’t get a problem because of this design flaw.

 

[Calimili]

It seems clear to me. They do not need to be able to guarantee that you will get a problem, to issue operating instructions to ensure you won’t get a problem because of this design flaw.

Adhering strictly to this interpretation, it means your available fuel is 60 litres if you have a 80 litres tank. They could have then re-calibrated the fuel gauge to show "Reserve" when there are in fact 25 litres left, rather than 5.
What's the point off having a fuel light coming up at 5/10 litres left, when you've already destroyed the dpf running the last 15 litres, or say, 100 miles...?

 

[Legin]

Lightning I know you do this to create argument of which Im not that interested this time round. Its clear that as always you actually have no technical contribution other than OEM knows best. Your faith in the architects of dieselgate seem unbounded.
I make these final comments on the matter so that others reading the thread can see all angles and make up there own minds.
Im not contradicting anything VW say Im explaining why they say what they do. Its far simpler to state keep above 1/4 than explain whats really happening.
What evidence do you have that VW knows best and has our best interests at heart ? None. Trust me they havent its just about money and reputation, they kicked the can down the road with fix.
You may not realise but the increased Ad blue fix is really dieselgate 2 but thats for another thread.
Suggest you go and read some of the detailed papers out there and join the diesel gate thread to gen up. Then you can explain technically why 1/4 tank all the time is a must.
You wont will you.

 

[Lightning]

Lightning I know you do this to create argument of which Im not that interested this time round. Its clear that as always you actually have no technical contribution other than OEM knows best. Your faith in the architects of dieselgate seem unbounded.
I make these final comments on the matter so that others reading the thread can see all angles and make up there own minds.
Im not contradicting anything VW say Im explaining why they say what they do. Its far simpler to state keep above 1/4 than explain whats really happening.
What evidence do you have that VW knows best and has our best interests at heart ? None. Trust me they havent its just about money and reputation, they kicked the can down the road with fix.
You may not realise but the increased Ad blue fix is really dieselgate 2 but thats for another thread.
Suggest you go and read some of the detailed papers out there and join the diesel gate thread to gen up. Then you can explain technically why 1/4 tank all the time is a must.
You wont will you.

I have no interest in creating an argument. Technically you may be right. Equally you may be wrong. I don’t know.

Having worked in engineering for large top level aircraft manufacturer for decades, I have seen this type of issue play out many times.

The manufacturer issues instructions based upon their incredibly detailed knowledge of their systems. The rationale for the decision is not often/ usually provided to the end user.
Without visibility of the rationale from the source, it is not really possible for the end user to determine if the rationale used to construct a procedure is sound. However, they often make their own mind up for their own convenience with variable consequences. It’s incredible how many people think they know best, without any competence to do so, even in safety critical aerospace issues.

If VW issue an instruction and the end user has no means of validating it. Then the end user has no real option but to trust VW.

It is not possible for either you or me to have more knowledge of the VW system than them. The instruction may be simplified, or it may be exactly what they intended. We don’t know.

To contradict their instructions, without possessing their knowledge of the system, moves the liability from them to us.

If you have links to documents specific to the current T6 emissions systems then I would be interested in reading them. If you have generic industry documents, then I would not know if they were relevant in this case.

 

[Sunstoner]

Does this same scenario / issue exist with the T6.1 ?

Can anyone confirm?

 

[B J G]

May be a stupid question but how do you know regenerate is taking place.

Idle speed goes up to nearly 1,000rpm. only noticeable at junctions etc obviously. I've got so that I check at most stationery points, brainwashed?

 

[Borris]

Does this same scenario / issue exist with the T6.1 ?

Can anyone confirm?

I don't know but I think you could safely bet your boots on that.

 

[Sunstoner]

I don't know but I think you could safely bet your boots on that.

Thanks @Borris

 

[Legin]

I have no interest in creating an argument. Technically you may be right. Equally you may be wrong. I don’t know.

Having worked in engineering for large top level aircraft manufacturer for decades, I have seen this type of issue play out many times.

The manufacturer issues instructions based upon their incredibly detailed knowledge of their systems. The rationale for the decision is not often/ usually provided to the end user.
Without visibility of the rationale from the source, it is not really possible for the end user to determine if the rationale used to construct a procedure is sound. However, they often make their own mind up for their own convenience with variable consequences. It’s incredible how many people think they know best, without any competence to do so, even in safety critical aerospace issues.

If VW issue an instruction and the end user has no means of validating it. Then the end user has no real option but to trust VW.

It is not possible for either you or me to have more knowledge of the VW system than them. The instruction may be simplified, or it may be exactly what they intended. We don’t know.

To contradict their instructions, without possessing their knowledge of the system, moves the liability from them to us.

If you have links to documents specific to the current T6 emissions systems then I would be interested in reading them. If you have generic industry documents, then I would not know if they were relevant in this case.

You will need to get into this private group EA189 Fix Reversal Assistance (VW Diesel Emission Scandal) Forum

Interesting your background as we likely worked for the same Aircraft outfit , I was in Engineering also. Im sure you are watching 737 Max with interest !
I worked even longer for one of the biggest Oil majors and it may or may not surprise you to know that some of the detailed testing is done by the Oil companies including all these systems. Camshaft design for F1, high temperature corrosion, dpf and so on.
Its not like Aircraft really as the expertise is in the fuel and lube side of the business for emissions. You get a clue with the trackside involvement in F1.

So actually I have worked directly with people and close to this stuff and way beyond the manufacturer much of the time. Also the big Oil companies as the one I was in do the full emissions certification , all the gear etc.
I cant say much more but there is more and it forms part of my understanding of what really goes on.

 

[bigmac77]

Other car is a diesel Macan and that forum has long running threads about people who have had problems with their DPF's, some needing forced regens that require cars being taken back to dealerships on transporters, owners with petrols saying the diesel buyers made a big mistake. Diesel owners stressing about possible ECU updates done without their knowledge by dealerships which they believe have only made their problems worse. Also Adblue, type of Adblue to use (should it have a -1 at the end of the number or not), should you self fill? (dealers recommend only they fill for you), how much to fill etc etc. The same advice re 1/4 tank of fuel is given by the dealerships. Any of this sound familiar?

Yet in nearly three years of ownership we have had no problems at all, we fill it with supermarket fuel when the fuel light is on, I fill it to the brim with Adblue when it tells me the tank is low and we have never had a problem with the DPF. The car does occasional short journeys of less than 5 miles but mostly is does a 20 mile journey with my wife on her commute to work.

 

[2into1]

The WelshGas long journey let it run from max to min is just fine and will not affect regens , the reason is the DPF will passive regen rather than force regen (injection of fuel) because the pre conditions are in place .

I think we've established this is wrong. The T6 doesn't passively regen. Blasting down the motorway may slow the relative creation of soot, but ALL the regeneration on a T6 is computer controlled and involves forced injection of fuel.

 

[Legin]

Normally an Adblue vehicle will be OK because the only mod was put in more additive as I understand it. The pre ad blue macans with fix file are the ones I would expect to have biggest problems ?

 

[Legin]

I think we've established this is wrong. The T6 doesn't passively regen. Blasting down the motorway may slow the relative creation of soot, but ALL the regeneration on a T6 is computer controlled and involves forced injection of fuel.

Wasnt aware of that. Are you sure ?

 

[2into1]

Wasnt aware of that. Are you sure ?

I think I am... Hence the use of 'think' above. Vwguru explained here somewhere when I vented my frustration at it 'always' choosing 1 mile from home after a 200 mile blast, and me walking away from it doing the hovercraft impression.

 

[Lightning]

Wasnt aware of that. Are you sure ?

And there it is.

 

[Amarillo]

They are trying to get to the numpties who REGULARLY run with fuel levels of 20L or less and wonder why they get problems with DPF Regeneration.

There are plenty of legitimate reasons why people might want to keep their fuel tank low, and only top up a little each refill. 70/80 litres is a refill limit not a refill target. For those reasons I think it is a little unkind to refer to people who would routinely refuel to under a quarter of a tank as "numpties". It wasn't until very recently that we learnt of the problems associated with routinely keeping the tank low.

 

[Gruff Evans]

We have had our van for about 16 months and haven't had any instructions issued by VW or by the dealer, either at the time of it's first service, or any other time. There is nothing about keeping the diesel above 1/4 full in the manual supplied with the vehicle (only a warning that you shouldn't let it run out completely!).
Whilst I will endeavour to take sensible precautions (such as outlined by WG), I think that VW would have a hard time denying a warranty claim based upon a failure to follow instructions that they have never issued to me, or made me aware of.

 

[Legin]

I think I am... Hence the use of 'think' above. Vwguru explained here somewhere when I vented my frustration at it 'always' choosing 1 mile from home after a 200 mile blast, and me walking away from it doing the hovercraft impression.

It actually makes some sense because the low Nox = lower temps hence the vastly increased EGR cooling so the post injection is required to get the DPF hot enough for coke burn.