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I have a 1 litre 3 cyl 95ps polo 2020, with just 30k on the clock.
I have been quite used to seeing an indicated 58 - 60+ mpg.
This has suddenly changed, and now shows a loss of approx 6mpg. Tyres OK - no brake binding - performance unchanged and good.
Suggestions please (Mass airflow sensor??) would be appreciated.
Thanks in advance
C

Possible considerations;

• Is that the long term mpg or for a specific journey / one or two specific journeys?

• Over what period / mileage / number of tank refills?

• Different brand of fuel? / possibly a bad batch of fuel?

• Is the mpg calculation from the car’s computer or your own manually calculated figure? If the former, could there be an issue with the car’s fuel computer?

• Any change in recent driving habits?; e.g. different driver(s), journey type(s), times of day driven, traffic conditions, routes taken, speed driven?

• Possibility that your car was performing a GPF regeneration? When this happens, there’s a noticeable impact (worsening) on mpg during the regen process.

• Some countries use winter blend petrol as well as winter blend diesel (not sure if we do in the UK or when the switchover date would be). Winter blend fuels tend to be less energy efficient than summer blend fuels, so mpg would be lower.

• Has there been a sudden drop in ambient temperature in the part of the UK you live / use your car?

Polonut wrote: Tue Oct 31, 2023 12:24 am I have a 1 litre 3 cyl 95ps polo 2020, with just 30k on the clock.
I have been quite used to seeing an indicated 58 - 60+ mpg.
This has suddenly changed, and now shows a loss of approx 6mpg. Tyres OK - no brake binding - performance unchanged and good.
Suggestions please (Mass airflow sensor??) would be appreciated.
Thanks in advance
C

That must have been the most comprehensive reply I have seen on this forum..

grazuncle2 wrote: Wed Nov 01, 2023 9:31 am

Polonut wrote: Tue Oct 31, 2023 12:24 am I have a 1 litre 3 cyl 95ps polo 2020, with just 30k on the clock.
I have been quite used to seeing an indicated 58 - 60+ mpg.
This has suddenly changed, and now shows a loss of approx 6mpg. Tyres OK - no brake binding - performance unchanged and good.
Suggestions please (Mass airflow sensor??) would be appreciated.
Thanks in advance
C

That must have been the most comprehensive reply I have seen on this forum..

I like to try and help other forum members if I can . It’s worth considering that a change in mpg isn’t necessarily a fault with the car, it could be due to one or more of the ‘external’ factors I included in my list.

It’ll be interesting to hear back from @Polonut on what the actual cause of their mpg drop was. @Polonut; it will also be worth monitoring your mpg over a number of tank refills to see if things improve over time. I don’t monitor my mpg too closely, but if my car performs a GPF regeneration, there’s a significant drop in short term mpg (e.g. the journey during which the regen happens and the mpg since the last tank refill). After the regen’s completed, things soon get back to normal.

Many thanks for the interest and comments.
Let me try to give a little more detail re my problem.
Firstly I am looking at individual journeys - and comment is based on the indicated MPG figure shown.
There is no loss of performance.
This happened about 2-3 weeks ago. The days use gave an INDICATED figure at end of journey as 60 MPG.
The next day (doing a repetitive journey) this dropped to 49. It was evident that it was a struggle to reach this lower figure.
In any week, there are two days when I drive 22 miles to destination, and after approx 3 hours
do the return trip. As ridiculous as it seems - this normally shows an INDICATED end of journey figure between 58 to 64 mpg. The journey is done on an ideally mostly flat road at 50 MPH.
Last week I did a 200 mile trip (Mostly on motorway) at 60-70 MPH - difficult to get around the 52 MPG figure.
IF it were a regen problem, it certainly should have completed by now.
In confirmation the LONG TERM and since REFUEL reported MPG figures have reduced pro rata.
As a point of interest, my earlier Mark 5 Polo also returned excellent mpg figures - and the mark 6 maintained this figure until a few weeks ago.
When rain stops !!!!! - I will take a look under the bonnet to look for any obvious leaks/disconnects etc. Will endeavour to look up mass airflow test procedure (Meter wise).
Keep the ideas coming
Thanks
C