I drive a 2009 Škoda Superb II; a 2.0 TDI with 125KW (170HP). The car has ran for 211K KM's (or 131K miles).

 

I've read up on the average MPGs for second generation Superbs and about the differences between actual brim-to-brim results VS the MPGs (or litres per 100KM) in the MFD.

 

What I've got, however, is a tad bit different.

 

In short - I've manually tracked the fuel consumption by re-fuelling at 1/4 tank. My average results have come up 6,4L/100KM (or 44,5 MPG using the UK gallon). However, the result shown by MFD is, on average, 5,7L/100 (or about 50 MPG). These results are based on 4 re-fuelings.

This is causing a problem - the MFD will show that I have fuel left in the tank even if I don't. I've stopped twice due to no fuel even though the MFD showed a range of 80 or 100KM. This is why I've always re-fueled at 1/4 tank - to avoid dangerous situations.

I commute 86KM (43KM to work; 43KM to home) per day taking the same route. 54KM (27 to the city, 27 from the city limit to home) of that is on highway at 100km/h with the rest being driven in the city.

 

Now, I know that the MFD is not 100% correct and should be off by about 5 to 10% - however I've never had a car which showed that there was fuel left in the tank when there actually is not.

 

I know that the previous owner(s) had done something of a tune on the car - which in reality should be offering better MPG (not getting that) and better peformance (haven't driven a pre-tune car; can't say). Could this be the source of this problem?

Does anyone have any experiences with this? To me it seems reasonable to assume it because more fuel is being used but the original parameters for "counting" the fuel used were left the same.

A local tune-shop has quoted me 300€ to revert the car back to it's original factory tune (if they have the original files). Currently I am thinking of getting it done the next month if I don't find a better solution.

 

 

You could get it back to a factory tune for free if you get the EA189 emissions update done at a Skoda dealer. If you find you don't like it then you could look at spending the money at a tuner.

2 minutes ago, chimaera said:

You could get it back to a factory tune for free if you get the EA189 emissions update done at a Skoda dealer. If you find you don't like it then you could look at spending the money at a tuner.

 

Should have added a bit more information to this; I apologize if this causes any confusion. Nevertheless...

This is interesting as the official Škoda dealer's workshop manager was "afraid" to revert the software back to the original for the fear of the ECU locking up. His rationale was that since they do not know what and how was exactly done they would not be 100% sure that the car would function after they would attempt to restore the software.

 

 

Hmm, that's a tough one to call. It might be worth seeing if you can get a replacement engine ECU from a scrapyard to swap in: depending on cost it might be cheaper than getting a tuner to look at the existing one.

 

Regarding the MFD/fuel consumption, there is an adaptation channel in the instrument cluster for adjusting the calibration of the fuel gauge: IIRC you drain the fuel tank then fill it with 9 l of diesel and adjust the needle position with VCDS until it sits just at the start of the red zone.

 

While a remap would change the information being sent from the engine to the instrument cluster regarding fuel use, it shouldn't have any impact on the fuel gauge. It's possible that a previous owner went messing with this calibration and got it wrong.

As above, I doubt the engine ECU has much to do with the fuel gauge.

 

If I remember correctly, the fuel level sender is connected directly to the instrument cluster. The cluster software does have a 'curve' programmed into it to account for different sized and shaped tanks.

 

Does the fuel light come on just as the fuel gauge hits the red zone? If so, it feels like the sender or wiring could be at fault :/

 

As for the emissions fix, the update should overwrite the remap regardless of what's currently installed but a half decent tuner is probably a wiser choice :)

1 hour ago, chimaera said:

Hmm, that's a tough one to call. It might be worth seeing if you can get a replacement engine ECU from a scrapyard to swap in: depending on cost it might be cheaper than getting a tuner to look at the existing one.

 

Regarding the MFD/fuel consumption, there is an adaptation channel in the instrument cluster for adjusting the calibration of the fuel gauge: IIRC you drain the fuel tank then fill it with 9 l of diesel and adjust the needle position with VCDS until it sits just at the start of the red zone.

 

While a remap would change the information being sent from the engine to the instrument cluster regarding fuel use, it shouldn't have any impact on the fuel gauge. It's possible that a previous owner went messing with this calibration and got it wrong.

This would affect the physical gauge; not the MFD displaying the consumption, right?

14 minutes ago, Rain said:

This would affect the physical gauge; not the MFD displaying the consumption, right?

Yes, but there's also an adaptation channel to correct the MFD display.

18 hours ago, langers2k said:

As above, I doubt the engine ECU has much to do with the fuel gauge.

 

If I remember correctly, the fuel level sender is connected directly to the instrument cluster. The cluster software does have a 'curve' programmed into it to account for different sized and shaped tanks.

 

Does the fuel light come on just as the fuel gauge hits the red zone? If so, it feels like the sender or wiring could be at fault 😕

 

As for the emissions fix, the update should overwrite the remap regardless of what's currently installed but a half decent tuner is probably a wiser choice

 

Can't check if the fuel light comes on as the gauge hits the red zone - afraid of having 0 gas on the tank.

 

I'll ask for quotes from the local tuners to see what the cost would be. Regarding the emissions fix - if I'd let the Škoda dealer do it I would have a chance to observe the results afterwards; if things go even more south than I always have the option of having my car tuned.

 

 

If the engine is turning off before the gauge is even hitting the red zone, that very much feels like a faulty fuel sensor.

 

 

How many litres of fuel does the car take when you fill up?

How many miles do you get from it?

 

Does anyone know how big the tank is on the OP's car?

 

Tank is 60 l IIRC. Should be in the manual too.

On 03/01/2020 at 13:31, langers2k said:

If the engine is turning off before the gauge is even hitting the red zone, that very much feels like a faulty fuel sensor.

 

 

How many litres of fuel does the car take when you fill up?

How many miles do you get from it?

 

Does anyone know how big the tank is on the OP's car?

 

 

Does not turn off immediately when it hits the red; the light comes on, however the calculation is way off - the turn off happens when the MFD says that I have about 100 or 80KM or range left.

Since I do not dare to go below 1/4 of a tank - the 1/4 to brim fills have given me an average range of 607KM (377 miles). I try to squeeze in as much as possible and I usually fit in 39 litres.

 

On 03/01/2020 at 15:09, chimaera said:

Tank is 60 l IIRC. Should be in the manual too.

 

This is another topic that I did not bring up here, but, I am sure that the tank is actually 50 litres.

I did not save the link but I remember reading up that for some reason the 60 litre tank was a free-of-charge option for the earlier Superb II models.

 

In any case I do not see the actually fuel tank size affecting anything here as I fill it to brim whenever I tank the fuel - even if for some reason there is 21 litres left in the tank when I re-fill (if we assume that it should be 60L and I usually squeeze in 39L) then the MPG won't change; I am still having the problem.

This would, however, introduce another problem of my car not being able to access almost 1/4 of the fuel tank. However, I would not focus here for the moment as the calculation ((60/6,4)*100=937) would say that I should be getting 937KMs (582 miles) with my bad MPG (6,4L/100KM; 44,5MPG). Which means that the car stopping at 100KM of range would be impossible unless 1/4 of the tank is not accessible - but, as stated, does not change the MPG as my re-fills from 1/4 to brim should show the truth.

I'm not that worried about the MPG being off, that's pretty normal. My car was around 13% optimistic until I tweaked the instrument cluster with VCDS. Given the figures of 44.5 vs 50 MPG, it's about 12% optimistic so certainly within the 'normal' range in my experience.

 

If the car is stopping at 100km range left, that suggests the car thinks there is at least 6-7 litres in the tank which would match with your ~40l refills and a 50l tank. This is not normal and is the problem you need to solve. For example, my Octavia has a 55l tank and I've frequently got 54-56l in at a fill up without the car stopping before hand. A handful of times the MFD has shown a range of 0 miles as I've pulled into the fuel station...

 

At the very least, I'd replace the fuel filter. I'd almost be tempted to grab a couple of fuel cans with fresh fuel, run the car down to the normal 1/4 tank, drain the remaining fuel in the tank as there could be some contaminates or other crud in the tank. Then replace the filter, prime the system and refill with fresh fuel.

 

I'm not sure if there is a second filter in the tank or any pipes/pickups that may be damaged of failing 😕

 

edit:

Just had a look online and there is a chance the Superb fuel tank is a 'saddle bag' style. If this is true, a failing/failed transfer pump could certainly cause this. Certainly worth having a look under the car to check what kind of tank is fitted...

Edited 6 January, 20206 yr by langers2k

35 minutes ago, langers2k said:

I'm not that worried about the MPG being off, that's pretty normal. My car was around 13% optimistic until I tweaked the instrument cluster with VCDS. Given the figures of 44.5 vs 50 MPG, it's about 12% optimistic so certainly within the 'normal' range in my experience.

 

If the car is stopping at 100km range left, that suggests the car thinks there is at least 6-7 litres in the tank which would match with your ~40l refills and a 50l tank. This is not normal and is the problem you need to solve. For example, my Octavia has a 55l tank and I've frequently got 54-56l in at a fill up without the car stopping before hand. A handful of times the MFD has shown a range of 0 miles as I've pulled into the fuel station...

 

At the very least, I'd replace the fuel filter. I'd almost be tempted to grab a couple of fuel cans with fresh fuel, run the car down to the normal 1/4 tank, drain the remaining fuel in the tank as there could be some contaminates or other crud in the tank. Then replace the filter, prime the system and refill with fresh fuel.

 

I'm not sure if there is a second filter in the tank or any pipes/pickups that may be damaged of failing 😕

 

edit:

Just had a look online and there is a chance the Superb fuel tank is a 'saddle bag' style. If this is true, a failing/failed transfer pump could certainly cause this. Certainly worth having a look under the car to check what kind of tank is fitted...

 

Thanks for the tip; I did not look at it this way but it makes 100% sense.

Also - I need to take back my "the tank is 50L statement" as it just makes no sense since all of the technical sites and forums indicate a 60L tank. This is a much bigger problem that I had thought; I'll get right on it. I clinged to it as it would explain the capacity that I am getting. You see what you want to see, right?

 

Regarding the MPG - I am still on the fence about it. I've had the pleasure of owning a total of 3 VAG cars in - all of them different MKs of Golf (and diesels!) - and while I never ran them dry I could always net a reasonable MPG with correlated with the MFD and with my fill-ups (2011 MK6 Golf 77KW diesel netted me an average of 5L/100KM which was fantastic!). Futhermore - the range indicator was never off and I could drive "safely" straight to a pertrol station when the MFD showed a range of below 100KM. I was constantly getting close to 1000KM or more on a single tank. This is one of the things that drove me to Škoda as it is, essentially, a VW underneath (shares a lot of components - the engine and so on).

A thing that bugs me a bit is that all the signs point to some kind of a fuel loss as I am hitting the avg. MPG rating according to my MFD (5,7L combined per 100KM) with the way I drive and the type of driving I do (3/4 on the motorway, 1/4 in the city - every day a roundtrip close to 90KM).