Lower MPG After Service/Software Update - BMW

[akorn]

Hi All,

Would like some advise regarding an issue I'm encountering with my car - 2017 BMW 340i petrol with 5,400 miles on the clock.

My car had a minor service and a software update by BMW couple weeks ago. Since then my mpg is sitting at 22-23, whereas before it used to be 29-32mpg.

I took it back to the branch for a re-evaluation but they said nothing is wrong and they are refusing to do anything else.

Could anyone advise on if its this normal and what could be wrong?

Thanks.

[E-bmw]

Have you done a tank fill/empty/fill to see what you are actually getting?

Did you do it beforehand?

If not then you really don't know.

There could have been a software update that made it more/less accurate, but that is unlikely to have ACTUALLY affected your real MPG.

[akorn]

E-bmw said:

Have you done a tank fill/empty/fill to see what you are actually getting?

Did you do it beforehand?

If not then you really don't know.

There could have been a software update that made it more/less accurate, but that is unlikely to have ACTUALLY affected your real MPG.

Thank you for your response. I haven't tried running it to empty yet - I'll give that a go.

If that fails, any idea what it could be? BMW have checked it over twice in two weeks and say there is zero faults with the car.

[E-bmw]

You do realise what I mean don't you?

You don't just run it to empty, you actually measure what you are getting.

But if you didn't do it before, you won't know if it has changed.

I think I said what it could be, didn't I?

if they are saying there isn't a problem, than maybe there isn't a problem, just a wild guess, like.

[GreenV8S]

In other words fill it, run it down to somewhere in the bottom quarter of the gauge. Fill it again. Make a note of the distance traveled and fuel needed to refill it. Then you have enough data to work out a meaningful average fuel consumption. By repeating it and averaging the results you can get even more accurate figures.

[AW10]

And make sure the units in iDrive are set to imperial (UK) gallons rather than US gallons.

[slybunda]

Software update probably stopped telling lies about your mpg and now your getting more realisitic results.
Never trust the onboard display. I always go by tank full to tankfull