Hi. 
I have recently bought a 125k 2016 superb 2.0 tdi 148 DSG estate L&K. The car is lovely, drives well, (apart from a slight suspension creak) and feels like it has good power BUT so far I have managed a best of 31.1mpg.  That is driving like a SAINT, in eco mode, on a long motorway journey (cruise @ 70) and a little gentle a road. 
min normal mode on 50/50 long motorway a road I got 29.9mpg from the second tank. Again, driving VERY gently and using cruise as much as possible. No traffic jams or city use. 

 

any ideas what I need to check? I bought it expecting to get a minimum of 46/47 mpg in open road driving and this is nuts

 

the other points that may relate are:

- Stop start only works very occasionally. Most of the time the engine stays running when stationary. 
- The cooling fan almost always runs for several minutes after parking up at the end of a journey. 

- I have had it on a fault code reader and the only fault I can see is that there is some sort of movable radiator blanking flap that seems to be not reacting to commands. 
- The DPF light came on toward the end of the first motorway journey in the car (about 200miles in) and stayed on for the next 40 miles or so until I parked. It was not in the next time I started and had not come back on since. 
- It seems to be using some oil. I don’t know where the oil was when I bought it, when I checked today it was low and needed 1.5l to bring it up to max on the dipstick. 
 

Tyres are Michelin cross climate (19”) at the correct pressures.

fuel is vPower diesel

the car has a full dealer history and is not due another service for 5k miles or 230 days. 

MPG is measured brim to brim over a full tank, not from the computer (which is showing around 40mpg)

Two things I forgot:

-the car is 2wd 

-the battery is a nearly new Yuasa 096 and when I put it on my smart charge shows as being fully charged and in good condition

 

What does the Full dealer service history show as having actually being done Is what matters.  Oil and inspection services each year or 2 is nothing.    Look see if a clean and dry air filter is fitted.    I suspect the poor fuel economy is the car using fuel doing regens.   As to stop / start the new battery might not have been coded to the car.  Has the DSG been serviced with oil changes at 40,000, 80,000 and 120,000 miles.   The full history should be showing work done as per schedule.  Was the brake fluid changed in 2019, or since then?     Things that are considered extras at Main Dealer serviced get done if paid for.  Even a car with a serviced plan might just get oil and filter changes and look see and reports.   Ps. Running low oil levels means the car is working harder to keep the oil to an efficient oil temp.  Also that checks were not being done.  Always check oil and coolant when cold when collecting vehicles, the. Again once at normal op operating temp.  That is once the oil is at an indicated 90*oC.  Not the coolant showing that. 

Edited 18 November, 20223 yr by toot

Thanks Toot. I will check through the history.

 

air filter is an obvious good shout. And I will check wheel temps after a drive to see if it has a binding brake.
I too think it is doing/trying multiple regens, but have no idea where to start at checking. My icarsoft diagnostic is pretty unusable when a car has this many systems, it grinds to a halt. 
 

I didn’t know that the batteries needed coded to the car. Pretty sure that didn’t happen. I’ll see if my diag is up to that. 
 

I am shocked that service essentials are optional on the dealer history. I will wade theo the receipts. I hear you on the other things. I will check, but things like brake fluid, while good shouts for longevity, are not going to be causing that mpg, and I need to start with the elephant in the room before it is worth considering anything else. 
 

I did check the fluids etc, but the dipstick had an ingrained oily soot deposit that looked like a full oil level even when wiped. Schoolboy error… Tbh, I shouldn’t have bought it in the circumstances. It was dark, raining and I was shattered. I had been to see what I thought was ‘the one’ and it was a complete wreck. This was an on a whim, on the way back detour because the car I had previously needed to be gone asap.
this one presented well, the dealer had excellent reviews, and the warranty package is good. I know the area it came from, which is a good one, and the stack of receipts is huge. (Shame about the dark brown leather tho😳)

@varooom might be able to give you advice on checking soot levels.  Lots of recent posts on the subject in different sections of the forum. 

13 minutes ago, toot said:

@varooom might be able to give you advice on checking soot levels.  Lots of recent posts on the subject in different sections of the forum. 

I was then posting such a thing 😄

 

 

Your most likely suspect for the poor fuel economy will be the near constant DPF regenerations, when you first got the car and done the 200 mile trip, it should have in theory been able to passively clear the soot, or put itself into an active regen mode to inject more fuel to burn off the accumulation of soot particles.  After an hour of trying to clear the DPF, or if the soot will not clear in that time while driving at motorway speeds, then it will put on the exhaust light, the next stage is exhaust light with limp mode.

 

Now in Km, you usually check oil ash at 230k Km, then every 30k thereafter as a rule of thumb.  This is not a measured value, but one that the ECU calculates, however if a car is burning more oil than average, then the 'real' value will be beyond what is claimed (by how much, you can only guess) as this value increases, the efficiency of the DPF goes out of the window, as it clogs the exhaust.  This creates more back pressure, making the car work harder = more fuel.

 

The next thing that occurs is the soot from unburnt fuel, this is what the DPF can actually burn off, but only if it is working correctly.

 

I would recommend you try to locate someone in your area that you can plug in your car and read out the following value in the engine ECU

Oil Ash

Soot measured

Soot calculated

 

You could in theory, if the person is happy to help, do what's called a 'static regeneration' on the DPF

Kinda noisy, so would recommend that you drive to a car park for example or layby where you can perform this process, make sure you have plenty of fuel in the car

 

While you have VCDS, you can check in the gateway of the car, and make sure the battery is adapted.

Most important are battery type: AGM / EFB / Wet *names in coding vary from the values

And the Ah rating of the new fitted battery, then last is to increase the serial number by 1 to make the car know it's a fresh battery.

Edited 18 November, 20223 yr by varooom

Thx so much Varoom. I will start and see if I can read those values with my diagnostic tool.  If not, there is one VCDS owner nearby and I’ll reach out to them. 
 

I will update the thread as I go. 

I agree with Varoom, you must as a matter of urgency sort out the blocked DPF causing the constant regens, that your oil level is going down and not up (which constant regens would normally do by thinning the oil with diesel) indicates that engine damage has already occured, piston ring & bore wear caused by bore wash.

 

I would change the oil straight away.

 

When things are sorted and assuming that the engine has a healthy compression then if your MPG is still not what it should be according to your driving style and journey profile then the next suspect would be the stepper motor throttle body and intake tract being clagged up from EGR soot.

So my diag tool did work (albeit painfully slow) and:

 

Oil ash mass: 57.60g

Oil ash volume: 0.14l

Soot calculated: 13.71g

Soot measured: 22.69g

Distance since last regeneration: 11658m

Time since last regeneration: 1120s

 

i assume that is not ideal…

 

History wise:  it has had 2 brake fluid changes,

2 out of the 3 DSG services (75k and last this year at 120k)

timing belt in late 2020 at 100k

no notes of previous issues of this nature. 
no notes of oil being bought outside of service time ( I have all records from the last few years down to odds and ends bought on eBay for the car. 
so I’m pretty sure this is not a known long term fault from the PO. 

That oil ash is 57.60g out of 80g iirc, however, that might be higher/lower as it cannot be measured, only estimated.

 

At your current soot measured, it will be definitely running regeneration, and if it cannot get to under 4.5g (roughly) the regeneration cycle's will never end.

 

At above 22g, the car will most definitely be putting itself into regen mode every journey.

 

 

You need a tool that can perform a static regen and monitor exhaust temperature and soot values during the process, like VCDS can.

Sounds to me like you've bought somebody elses problem, can you take it back?

 

It doesn't seem to add up that the last regen was 11658m, which is presume is meters?

 

I would try and see if you can view the live data or even better, log the data from the DPF temprature sensors and pressure also. When you buy a car that already has issues they could of of done something stupid such as remove the DPF without mapping it out, or let the DPF fill up to near breaking point.

I have had the car a fortnight from the selling dealer. I am leaning toward money back and return it, or they pay for a dpf remove and clean. The issue is that I PX’d against it and I really don’t want that car back. 😂

 

I need to see if my diagnostic tool can force a regeneration as a starting point. 

The DPF is blocked, 18 minutes and 11km since last regen which failed, that the measured soot is pretty much double the calculated is very bad indeed, when mine shows a calculated 22 grammes the measured will be 4 or 5 grammes.

 

That and the high oil consumption points to it being offloaded via PX by the previous owner due to the cost of repairs.

On 17/11/2022 at 22:04, Brianjuk said:

Hi. 
I have recently bought a 125k 2016 superb 2.0 tdi 148 DSG estate L&K. The car is lovely, drives well, (apart from a slight suspension creak) and feels like it has good power BUT so far I have managed a best of 31.1mpg.  That is driving like a SAINT, in eco mode, on a long motorway journey (cruise @ 70) and a little gentle a road. 
min normal mode on 50/50 long motorway a road I got 29.9mpg from the second tank. Again, driving VERY gently and using cruise as much as possible. No traffic jams or city use. 

 

any ideas what I need to check? I bought it expecting to get a minimum of 46/47 mpg in open road driving and this is nuts

 

the other points that may relate are:

- Stop start only works very occasionally. Most of the time the engine stays running when stationary. 
- The cooling fan almost always runs for several minutes after parking up at the end of a journey. 

- I have had it on a fault code reader and the only fault I can see is that there is some sort of movable radiator blanking flap that seems to be not reacting to commands. 
- The DPF light came on toward the end of the first motorway journey in the car (about 200miles in) and stayed on for the next 40 miles or so until I parked. It was not in the next time I started and had not come back on since. 
- It seems to be using some oil. I don’t know where the oil was when I bought it, when I checked today it was low and needed 1.5l to bring it up to max on the dipstick. 
 

Tyres are Michelin cross climate (19”) at the correct pressures.

fuel is vPower diesel

the car has a full dealer history and is not due another service for 5k miles or 230 days. 

MPG is measured brim to brim over a full tank, not from the computer (which is showing around 40mpg)

Hi Brian, one point to note - cruise will not generally give you the best fuel economy possible.

So I found a secluded industrial estate road and did a forced regen with my icarsoft diagnostic tool.
all a bit odd. 

The regen started:

turbo upstream temp climbed to 560deg

temp before particle filter climbed to 640deg

Temp after particle filter climbed to 592deg

thw temps stayed pretty static for an hour or so and then the revs dropped and all 3 temps dropped to the 130s but the regen never showed as complete. After about another 30mins at idle with similar temps I gave up and cancelled it. 
 

post aborted regen the situation is worse:

calculated soot is now: 0.17g

measured soot is now: 25.80g

ash is the same as before. 
 

i am thinking next steps is to book it into a local VAG specialist for proper diagnosis, because I will need paperwork to hit the dealer with for whatever my next steps are. What do you think?  

Hi Brian, how far into the warranty period are you? I'd seriously consider rejecting if you can - or at least flag the issue to supplier.

Edited 19 November, 20223 yr by Warrior193
extra comment

7 hours ago, Warrior193 said:

Hi Brian, one point to note - cruise will not generally give you the best fuel economy possible.

Thanks. I do understand that, but it lets people know how it was driven. If I keep it, once the dpf is sorted, I need to retrofit a speed limiter (missing because I have an early ACC) and then I’m happy to drive it by foot and see what MPG I can get. 

1 minute ago, Warrior193 said:

Hi Brian, how far into the warranty period are you? I'd seriously consider rejecting if you can.

I have owned it for two weeks. The warranty is a year. I assume rejecting it will be harder the longer it goes.
 

I’m torn about doing that because the dealer does not have an alternative car I’d take and does still have my old car which I really wouldn’t want back.  I’d have to somehow get cash while leaving my old car there. If I could get this one properly fixed that would be my preferred option. 

3 minutes ago, Brianjuk said:

I have owned it for two weeks. The warranty is a year. I assume rejecting it will be harder the longer it goes.
 

I’m torn about doing that because the dealer does not have an alternative car I’d take and does still have my old car which I really wouldn’t want back.  I’d have to somehow get cash while leaving my old car there. If I could get this one properly fixed that would be my preferred option. 

Have you advised supplier of the issue yet?

Just now, Warrior193 said:

Have you advised supplier of the issue yet?

Writing that email now. 👍

Sorry to hear the static regen didn't go as expected, I had an issue with my 1.6TDi green line where it was stuck trying to regen all the time.  The regen ran, but the soot measured hit at wall at 15g, and couldn't drop lower.  The suspicion was that it had been used for too many short journeys, and the soot was kinda 'baked' on a little.

 

I have a friend who put in some DPF cleaning solution that after treatment allowed the soot measured to actually drop down to 1-2g, not saying this is what you need right now, as you need to push back on the vehicle supplier and see what they say (I hope you took screenshots or pictures on phone of the regen values earlier)

 

 

Keep us in the loop, and let's see what happens next together.

Have you tried looking at the raw value of the DPF pressure sensor with the engine off to verify its zero calibration and that the sensor is good?

Having tried forced regen, and car virtually permanently trying to unsuccessfully regen, it is clear it is only shifting the recent soot.   There will be long term baked on soot which you are just wasting fuel trying to shift.

 

A bottle of DPF cleaner might shift a bit more soot, but probably won’t clean it up that much further, and not enough to stop almost continuous regens.  I suspect previous owner did lots of short journeys, clogged it long term, and offloaded it.

 

In it’s current state the only way to sort the problem will be a removal and full clean by ceramex process or similar, or a replacement of DPF.   You can either let supplying dealer fix it, give you the funds to get it fixed, or reject it.  

 

Sorry but it looks like you have been sold a car with a major problem which was present at time of sale. At least you bought it from a motor dealer and legally it’s their problem, if you had bought it privately effectively buyer beware and no come back.

 

I'd say go back to seller and accept no less than replacement dpf.

And what about the 1.5 litres oil consumption in a very short time?

 

We dont know how long or how many miles but the OP did say recently bought.

 

I have driven half a million miles with 3 Skodas and only used 0.5 litres of oil in total, that was on the MK1 1.9 TDi ASV engine where the rings only bedded in after 200K miles and the consumption ceased, also I had gone way beyond the scheduled  oil change.

 

Return the vehicle for a refund or you will regret it dearly, this is probably just the beginning of many problems.