Mpg different to app

[Primus1]

On the cars speedo it shows 65mpg, yet on the app it’s showing 70.9 mpg, which one is to be believed?

[Guest]

Might I suggest  neither?

The only accurate way is a brim to brim fill up, zero a trip meter or record the total mileage and calculate litres/gallons to refill with the distance covered. Distance divided by volume of motion lotion added.

Possibly, if it's that important, more than once.

[Primus1]

Yes I know that’s the only accurate way for true mpg, but it’s a nice feeling to see the low fuel consumption figures..

[Roy124]

MyT is in agreement with fuel, range and mpg. 

[Graham47]

1 hour ago, Primus1 said:

On the cars speedo it shows 65mpg,

What is showing on the cars speedo (presume you mean “central display’) ?
Is it tank average ?/average since reset ?/trip average ? (which is what the app will show).
 

Are you comparing the same figures ?

[Primus1]

48 minutes ago, Graham47 said:

What is showing on the cars speedo (presume you mean “central display’) ?
Is it tank average ?/average since reset ?/trip average ? (which is what the app will show).
 

Are you comparing the same figures ?

Yes, central display, it just shows as fuel consumption mpg..

[Graham47]

That’s the reason then.

The display is almost certainly “since last reset” whereas the App reports avg. consumption for the single trip.

Suggest you study the owner’s manual for how to change the central display and the ‘pop up’ content which appears when you switch off the car.