Lost 10mpg after visit to dealers

[Robbydazzler]

As the winter kicks in, I also noticed a ~0.5L/100km increase (sorry for the metric units :p ) in the consumption of my diesel. For someone who mainly does short trips it should be very noticeable.

 

Now, GoneOffskiroottoot's is an apposite remark as it never crossed my mind that there may be a difference in the tyre size. A larger diameter wheel would travel more distance per revolution, leading the car computer to think it travels less, hence lower mileage.

I am confused! I thought all wheel/tyre combinations ended up with the same circumference/diameter as the profile of the tyre was adjusted to achieve this.In this way the accuracy of the instrumentation is maintained?

[RickTT]

I am confused! I thought all wheel/tyre combinations ended up with the same circumference/diameter as the profile of the tyre was adjusted to achieve this.In this way the accuracy of the instrumentation is maintained?

 

that is correct... but if a garage ordered the wrong size and fitted it could be possible. but then the speedo will be out, very rare, TPS erroring if mix matched

Edited 9 December, 2015 by RickTT

[Paulatic]

I was given the choice of three tyres nothing from anything they would have in stock. From the coding on the invoice I would guess they have an arrangement with Gates tyres ( only a guess) I didn't go for Dunlop because of my last experience. I buy a 6mth old car every ten years, my last was a Toyota Corolla came fitted with Dunlop Sport. They did 25,000 Mls I thought them excellent so I bought the same tyre again and the next set did barely 15,000. So I believe that tyre dealers might well be supplied with different quality to manufacturers. I didn't want to chance that disappointment again so went with another "first line" tyre.

To the the suggestion of winter weather it's been mild of late and doesn't explain the sudden change. Also doing a tank to tank check doesn't prove anything to me as I'm taking my figures , before and after, from the car. Yes I know a tank to tank will give me a truer reading.

Taking the car in, 35 Mls , ave 70mpg, bringing it home 4days later 54mpg. Coming back is never as good, it's uphill, usually around 68. I put that down to the fact it might have been idling around the garage. I've had two trips to Dumfries now, a weekly shop thing, and both have shown at 59mpg For a year now that trip would always show as 70 and if stuck behind traffic at 50mph it would be 75.

Looking at a web site today https://ec.europa.eu/energy/sites/ener/files/documents/FIN%20User%20guide%20-%20tyres.pdf they state a difference of 5% between best and worst fuel rating. The Firestone is E I believe so even if the Dunlop was in A that's not a full 5%.

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[Ootohere]

^^^^

Good stuff.  Its good when a driver knows their routine and economy.

 

Who at the Dealers told you no Update was done to the ECU, the Service Desk Staff, or the Master Tech or Workshop manager?

& what is the tyre size on the car,

and what pressures have you set them at.

[Paulatic]

Size is 185 60 15 pressure 2.3 bar

Just had a look at the spare and the old tyres were Dunlop Sport 01. Looking at their web site they fuel rate that size as F Making the Firestone a whole letter better so what the hell is going on here.

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[WillJohnson]

You sure its not just cas its got cold? I've lost 10-15mpg when it started getting cold? Well i've also found having the climate on 22+ kills yer economy too... and high winds.... These are all disadvantages of having a small petrol engine...

 

For example

-142 mile trip to grimsby @12 degs c with no wind  = 56.6mpg

- 142 mile trip back to preston @ 5 degs c and STUPID winds = 39.9mpg (Might as well buy a V8 if conditions are like this all the time)

 

Its unlikely its your tyres if your pressures are ok.

Edited 10 December, 2015 by WillJohnson

[Paulatic]

It's not got cold has it? 10.5C yesterday here I think June the 21st was a lot colder here.

Yes I agree wind can have a great affect I haven't used any windy day figures in my summary. When towing the caravan we went to Shropshire and back , in September, with good weather. Returned 37mpg. Came back from Penrith in July on a windy day returned 29 mpg

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[Ootohere]

?

So who at the Dealership told you that no Software Update was done while your car was in the Workshop,

Service Desk Jockey, Service or Workshop Manager or the Technician that worked in the car?

[Paulatic]

Service desk jockey.

I've written to them this morning, via email, with my history and evidence.

I'm sure someone is looking into this or scratching their head right now.

I await their reply with interest.

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[Ootohere]

Good.  Best get them to confirm in writing.

 

Just in case Skoda / VW had a wee 'Software Update' Enhancement' 'Trial Fix' they wanted to put on some cars to see how it works out.

[CosmicCowboy]

If you want good mpg buy some lrr tires.

[Ootohere]

Welcome to the forum.

 

Is that Low rolling resistance 'tyres',  if in the UK?

 

Like ECO tyres.

 Low grip / friction ones as many manufacturers use OME to have the Co2 / MPG EU Tests look like the vehicles is less polluting and more economical!

 

..................

Paulatic,

Since you have 1 of the original tyres on the spare, could you be bothered to take it out and compare side by side 

with what are on the car now, just to see they are physically very similar.

Edited 10 December, 2015 by GoneOffskiroottoot

[silver1011]

Welcome to 'Winter Diesel'.

 

It has a higher benzin content than summer diesel. The benzin reduces the tendency for the fuel to wax at lower temperatures. The additional benzin content reduces the calorific value of the fuel, so for a given volume of fuel you will get less energy out of it - hence lower MPG.

 

+ colder temperatures,

 

+ new tyres.

Edited 10 December, 2015 by silver1011

[Ootohere]

Winter diesel in Scotland was distributed from mid October, so either the tank of the car was only recently filled or the filling station tanks were.

 

As the OP said the ambient temperatures did not drop really.

And colder air means better and more efficient driving, and sometimes lower speed and less grip (friction) on roads.

 

Balanced by, letting car heat up, rear screen on, heated mirrors, radio, light etc, slower warming up.

But as the OP said, the weather was not really much cooler. actually August was quite cold.

[Paulatic]

I can now give you an update:

The new tyres were a whole "letter" better than the old ones in fuel rating.

I went back to the dealer armed with this information and said I needed a better explanation other than a change in tyres.

We went through everything that had happened. The saga began with calling Skoda Assist and I think this is where something occurred.

An AA man quickly arrived armed with a brand new toy he was eager to get out the box. Plugged in his new Bosch fault finder and played with every menu he could find but the windows aren't on there. He then disconnected the battery for a while hoping to reset everything.

It then went to the dealers and got new window motor fitted.

So they took another look at it and then said that an update was missing from the Ecu. I brought it away and at first it looked like mpg was exactly the same. Out in it today on a regular trip and mpg is now very close to what it was before it all started. Seems to be improving from learning my driving again.

[Ootohere]

Cheers for that.

 

Are you saying that a Dealership Technician 'Has done a Software Update to your Engine Management', saying they replaced a missing Update?

 

Maybe ask them next time to show you the Details of the 'Update; when this 'Update' was first available on the System.

It sounds like BS from the Dealership where an Employee told you something very different.

Post #34

Edited 28 December, 2015 by GoneOffskiroottoot

[Dr Zoidberg]

I think I'd be asking them to put in writing a detailed explanation of what they did both times, and then see what skoda have to say about this.

[Ootohere]

It is far too far fetched that Skoda are trying out 'the fix; on Customers cars with 'Software Updates' prior to the Authorisation to do that from the relevant Authorities and Vehicle owners.

 

That would just be a step too far for the Volkswagen Group to try and pull.

[Paulatic]

The words were an update was missing. Is it possible the AA man lost it?

Had a letter about "the fix" it's to be a fitting of a "flow transformer" directly in front of air mass sensor.

May be BS but mileage is definitely creeping up. I bought this car at 5000 mls it seemed to be 10000 before excellent figures were being achieved. At 20000 now I've had a long time to get used to seeing figures for regular journeys. Today's journey would be 2-3 less than expected but a whole 8 better than ten days ago.

[sparky2]

Hi Paul, Do you think that disconnecting the battery has reset the ECU to default settings, and its now learning about your driving style eg economy ? or VW group are trying out a software fix early ! cheers Stuart

[SaxophoneMn]

I had a similar problem.  We had very bad dust in Israel this past summer.  I had my 15,000 km maintenance done and then I barely ever see 24km/l (68mpg).  In the summer I once got 30 km/l (85mpg), helps that most of the ride is down hill.  Anyhow do you think that they're already doing the repairs on the 1.6 TDIs to have lower emissions?  We don't get much below 5°C, and I'm not sure if we're running a winter diesel but the price is much cheaper than usual.

 

During my maintenance they replaced the diesel filter, the oil filter, and the aircon filter.  My coolant was low, but I never passed the 90°C mark on my oil temp indicator, thought the warning light sometimes came on.  My tire pressure is kept at 32 psi, but had it moved up to 33 psi since I sometimes have a full car.

[harisma23]

I had a similar problem.  We had very bad dust in Israel this past summer.  I had my 15,000 km maintenance done and then I barely ever see 24km/l (68mpg).  In the summer I once got 30 km/l (85mpg), helps that most of the ride is down hill.  Anyhow do you think that they're already doing the repairs on the 1.6 TDIs to have lower emissions?  We don't get much below 5°C, and I'm not sure if we're running a winter diesel but the price is much cheaper than usual.

 

During my maintenance they replaced the diesel filter, the oil filter, and the aircon filter.  My coolant was low, but I never passed the 90°C mark on my oil temp indicator, thought the warning light sometimes came on.  My tire pressure is kept at 32 psi, but had it moved up to 33 psi since I sometimes have a full car.

You should have changed the air filter also, because in dusty environments (I live in Greece) it will not perform as it is supposed for 30,000 Km. I had mine checked after 16,000 Km and it was seriously clogged, so I chanded it. That made an impressive improvement in low revs. Every morning the car starts in a subterranean garage and has to climb a rather steep incline, after a very tight turn. Prior to changing the air filter, the car was struggling, but after the change the car was significantly more responsive.

A clogged air filter should also increase fuel consumption.

Edited 13 January, 2016 by harisma23

[SaxophoneMn]

I think I also had my air filter changed.  It was a bunch of filters. And a lot of money :(

[Paulatic]

Hi Paul, Do you think that disconnecting the battery has reset the ECU to default settings, and its now learning about your driving style eg economy ? or VW group are trying out a software fix early ! cheers Stuart

Yes I think that's what has happened. It seems to learn driving styles so I'm told. The ECU forgot me ? Probably due to the AA man and his new toy and totally not seeming to have a clue [emoji23]

There, I've said it now