Hi everyone 

 

Got a ‘17 plate 1.4 tsi DSG. Normally get 55-60mpg on a motorway run (where it generally sits), but couple of days ago it dropped to around 47, also on the motorway (and having done 58 ish that same morning!)

 

no change in my driving style and can’t say there were more hills than normal. Obvious stuff like tyres etc only recently pumped up. This year it’s had new sparks & ignition coils, air filter, oil & filter change. It has been saying “inspection now!!” in a very Germanic manor on ignition start up/off, but I’ve not paid notice to that as I presumed that was per the Skoda service schedule. Any one else had this experience? 
 

I should add there are no warning lights, and car still runs absolutely fine. I’ve got it in with a garage and waiting to hear the results of their plug-in test. Could it be clogged injectors (worth trying a fuel cleaner/additive)? Or just the sign of this new crappy jungle juice we’re having to deal with…seems strange it’s so sudden. Apparently the fuel filter is lifetime fit. Dodgy oxygen sensor perhaps? 
 

Thanks for your time

Ed

Instead of additive why not try a full tank of Super Unleaded so 97 / 99 E5 petrol with its additives.

Reset the computer and compare with the last tank fill.

 

That is if you have bought & used 95 ron E10 since it was introduced in September.       

(OT Winter Grade Petrol of Unleaded or Super Unleaded might be in your local filling stations depending where you are in the UK, starts in mid October in Scotland / North England.)

3 hours ago, EdHilton said:

Dodgy oxygen sensor perhaps?

Use the Search facilities, with a search string of "E10".

We need a scan.....ODBEleven or VCDS.....

Thanks very much for your replies guys. Unfortunately couldn’t get a printout from the VCDS scan but the garage I took  it too said there were no fault codes whatsoever. Have run a tank of Shell Premium E5 through and has sat mostly on the motorway and it seems to be OK- back up in the mid-high 50s.

 

Could have been a dodgy tank of fuel? Also since I bought the car in March I haven’t really been driving when the outside temp drops down to 3-4 Celsius yet, and on reading one threads that usually causes a slight drop in economy.

Yes, MPG will suffer when it gets colder. My personal recommendation is to use a product that I found from a company called Hydra International based in Milton Keynes. It cheaper and wi give you super unleaded performance for a lot less cash. 

https://www.hydra-int.com/petrol-power-blast.html

 

8 hours ago, EdHilton said:

Thanks very much for your replies guys. Unfortunately couldn’t get a printout from the VCDS scan but the garage I took  it too said there were no fault codes whatsoever. Have run a tank of Shell Premium E5 through and has sat mostly on the motorway and it seems to be OK- back up in the mid-high 50s.

 

Could have been a dodgy tank of fuel? Also since I bought the car in March I haven’t really been driving when the outside temp drops down to 3-4 Celsius yet, and on reading one threads that usually causes a slight drop in economy.

 

E10 unleaded 95 RON was introduced in September and has a reduced calorific value compared to the E5 95 RON so you would see a reduced mpg. My wife's Panda had to have a tank of E10 during the fuel crisis and it's MPG is indeed lower than usual.

 

Super unleaded is still E5. Myself I prefer Tesco Greenenergy which is 99RON and not that much more expensive.

 

@EdHilton in my opinion there is an increased risk of filling up with a 'bad batch' of E10 fuel so it does not surprise me that the poorer consumption you experienced was limited to the one fill.

Ethanol absorbs water more readily petrol so if there has been any contamination in storage or transport then the two components will separate and become layered.

There are a couple of things to consider if that has happened;

- If the separation occurred in the suppliers tank then you may have either greater amounts than 10% Ethanol, so potentially much lower calorific value, more fuel burnt and poorer consumption.

- or lower than the prescribed 10% Ethanol and the petrol component then falls below 95 RON rating and so again poorer performance and consumption.

- I presume that separation can also occur in the fuel tank but I am not sure what effect sloshing during car movement has on the potential effects I've described.

 

Pure Ethanol has a naturally high octane rating so adding 10% contributes about 3 RONs enabling the refineries a proportionate reduction of their normal anti-knock additives.

In normal use the 10% Ethanol fuels slightly lower calorific values are barely noticeable and some Briskoda contributors even report improved consumption with E10 but I'm not sure how that works.

General advice is to simply try to buy fuel from high turnover vendors.

 

In fairness it should be remembered that even low ethanol fuels can go 'off' over time as the volatiles (up to 30% of the mixture) will disperse and the remaining fuel is slightly compromised in quality. I've seen recommendations as low as a month for petrol storage before deterioration occurs, although longer most professional storage facilities.

Diesel is also hydroscopic and has been known to grow moulds over time.

 

I have no idea whether the absorbed water has any negative effects other than initiating the separation, but  presume not.

 

These are only my opinions and I would welcome correction or confirmation from knowledgeable professionals. 

 

from what I've read (bear in mind this is just from browsing sites on the internet) fuels with ethanol have a lower 'storage' life of around 3 months (depending on the ratio).

 

Full fat petrol is around 6 months.

 

Basically, 2 things which affects fuels in general; oxidisation and water intake. The problem is ethanol is affected quicker.

 

From my own experience with the limited running in the first lockdown, diesel starts going bad after 3 months. I had a fair tank full of winter diesel still in the car and even in the much warmer months of July, it wasn't sounding the best. I put a stabiliser in the tank just to keep things ok at the very start of the pandemic because I knew I was WFH til otherwise told.

 

With regards to fuel mixing in the tank whilst driving, I understand it will slosh about. Though I know there will be some kind of baffle, albeit it not as advanced as a racing tank, to stop fuel starvation.