Fuel economy on my Superb Sportline has dropped from about 32mpg to about 18mpg for the same journey overnight. It seems to have also coincided with filling up with petrol (coincidence?). Also, the start stop is no longer kicking in. Just got back from the dealer who says nothing is wrong except the battery was a bit low so they charged it up and start/stop worked for them. Journey home and the start/stop didn’t kick in once and the fuel economy was still shocking. 
 

Anyone got any experience of a similar problem? The people you speak to at a dealership are sales people, not the technicians. I just got accused of changing my driving style overnight. 

Is it actually using 4.5462 litres every 18 miles or is that what the computer is showing it is using?

 

Why not ask to talk with the Master Tech, not the Service or Workshop manager, a salesperson or the likes?

 

?

What was the petrol you filled with was it a different brand from a different place

& do you use 95 ron, or 97 or 99?

?

What age is your car and how many miles has it done?

 

 

1 minute ago, e-Roottoot said:

Is it actually using 4.5462 litres every 18 miles or is that what the computer is showing it is using?

 

Why not ask to talk with the Master Tech, not the Service or Workshop manager, a salesperson or the likes?

 

?

What was the petrol you filled with was it a different brand from a different place

& do you use 95 ron, or 97 or 99?

?

What age is your car and how many miles has it done?

 

 

The mpg I’ve stated is from the onboard computer. I’ll be doing my own assessment next. 
Fuel is 95. It’s only ever had 95. Filled in a BP garage that we haven’t used before. 
Registered nov ‘19, owned since aug’20. 9500 miles (3500 by me)
The service light has never come on but the garage said the electronic log indicates it hasn’t been serviced, says it is due in May ‘22!

You are as well to brim it and then see what the actual consumption is over the next 100 miles or so.

A bit early for a Air Filter replacement but looking to see how clean it is is worth doing.

 

Do you want to leave it on Variable / Flexible Servicing.  

?

Was it a Demonstrator / Ex Management car?   Surely they must have done some servicing before the sale to you.

 

Registered November 2019 means the first Variable Service is due November 2021 even if it was in a Showroom for months.

 

If due May 2022 then the service indicator was reset May 2020.

Think it was ex management. I’ll be ringing the guys I bought it from to get them to add the sales service they said they would do the the record. 
 

Hoping it’s just a dodgy fill up so I’ll run it down then brim it. I’ll check the air filter. Thanks roottoot. 

The battery voltage is a prerequisite indeed to allow the Stop & Start system to shut the engine down. 
There´s a ´start limit voltage´ parameter, which is set to 7,6V as a default value. This is a minimum value, but it can be tuned. The higher it is, the less the S&S will shut the engine down.

May be a long shot but stickibg brake calliper?

Jack each corner in turn amd see if the wheel turns freely.

Thinking to something else: How many miles has your car on the clock? Has the fuel filter ever been changed (every 90000km according to the service plan) ?

Potentially, if'you refueled at the "wrong" time, you may have fueled right after the gas station had been replenished. The gas station tank had just been stirring and you've injected some dirt from the bottom of the tank. Each time I see a tanker at the gas station I delay my refueling to avoid that.

 

May be it's the root cause... may be not. Just trying to help.

Filling station underground tanks have filters & water traps and so do the forecourt pumps. 

They will be serviced as they are fuelling thousands of vehicles regardless of the level of fuel in the tank.  Hopefully in the UK none are dispensing H20 anymore from condensation in tanks. 

Edited 22 May, 20215 yr by e-Roottoot

You're surely right. However, I'm not making allusion to H2O or condensation.

I'm more thinking of dirt that would be stirred during gas station tank replenishment and would have not enough time to fall back to the bottom of the tank by settling. It may clog a fuel filter for instance. I've read 2 or 3 threads (on french forums) of VAG engine problems after refueling... Probably very rare, I give it to you. But... **** may happen.

 

Sh!t caught in filters might happen,

but how would that increase fuel consumption other than when it is clogged air filters?

 

@jonsym might be able to tell us how they are getting on now with the fuel consumption.

 

New tanks sitting today at my local filling station.

Edited 23 May, 20215 yr by e-Roottoot

May be a bad hyptohesis... Just trying to find an explanation... I may be wrong.

I wonder if it's got miles and km confused somehow - 32km being 20 miles, not far off your 18. You could try changing units then changing them back again. 

If units had been changed to km, then I assume fuel consumption would be in l/100km, instead of mpg, wouldn't it?

@jonsym, I sympathise with your almighty consumption drop, and the lack of assistance or even empathy from the dealers.

 

I've got a couple of questions and suggestions for you:

Is your car fitted with a PPF? What is your recent 'normal' sort of journey (distance, speeds, highway or town)? 

The latter question is less relevant if no Petrol Particulate Filter is actually fitted.

 

Someone has already suggested that your car system setting may have been changed by accident to metric but as pointed out by another that would be pretty evident (we run metric settings in Australia)...however you may want to check that it has not been changed accidentally to American gallons which are smaller than Imperial (British) gallons as that would be much less obvious. US gallons was/is an option on both my mk2 and mk3 Octavia.

 

Assuming the measurement has not been changed and the reading is accurately reflecting higher consumption then it is possible (but admittedly unlikely) the fuel was contaminated.  I would expect the car to be running really badly and barely able to tick over if the fuel was that bad.

 

I can't see how Stop/start operation would be affected by bad fuel, well it would stop, but not start again. if the dealer only topped up the battery and did not actually test it then it may be worthwhile getting it checked.

Stop/start can be hard on batteries and there have been a few reports in Briskoda of premature battery failure. Probably depends on the usual journey type and maybe what happened to the car over lockdown?

 

Very unlikely it is the air filter, degradation tends to happen over a longer period, not overnight. Fuel filter? again I'd expect the car to judder or stop from fuel starvation, not just worsen consumption.

 

Assuming none of the above it may be worth your while contacting the selling petrol station and registering a complaint (hopefully bought on credit card for confirmation).

1) it registers that you recognise a possible problem with the fuel they supplied and if it manifests in later possible engine issues then it strengthens your claim for compensation. 2) Others who have filled there may have had the same problem and reported their issues which may prompt an ethical company to be proactive (don't hold your breath for that). In fairness what they don't know they cannot investigate.

 

I know two separate incidents in our tropical Northern Territories where contaminated diesel fuel was sold from individual stations (pumps?)  and numerous vehicle engines were damaged. It was only the the fact that the NT equivalent of the AA or RAC were able to collate the increase in call outs that they were found out and the vehicle owners compensated. In one of my mate's case he did unexpectedly well out of it when all the inconvenience factors were thrown in 

 

Edit: Just another thought: I don't know all the details of the UK lockdown and release but UK 95 octane fuel has a legal requirement for 5% Ethanol  content which is not usually a problem but IF the fuel had been stored for an excessively long time (lockdown closure and /or lower general fuel use) and IF storage had been slightly compromised (allowing some moisture contamination) then the ethanol and petrol would separate and you MAY have been unlucky enough to fill with a less than optimal mix? A lot of 'IFs' but you would think the next fill would resolve the problems.

 

Edited 28 May, 20215 yr by Gerrycan

An update. Seemed to improve a bit after the garage visit. The big change was a couple of decent blasts along the motorway. Yesterday I even managed 50mpg (according to CPU) on a 70 mile journey. I think with all this lockdown nonsense the car just hasn't been driven enough. This is certainly the case for the stop/start, I don't think the battery was getting topped up enough between starts so the stop/start was quite rightly deactivating. Traffic has been increasing with the easing of lockdown so that may have affected it too.

 

To answer some of the suggestions:

Airfilter was fine.

Petrol 'seemed' fine (no other local complaints)

Brakes ok, this was something I asked the garage to specifically check but also checked myself (none were overheating after a short drive).

Computers ok (Can't even find where to change it into metric! But is on imperial).

 

Thanks all for your suggestions/advice etc. Now to the Fabia VRS forum to sort the little car out!