Trip Computer Issue

[Foci888]

I recently bought a 2012 mk3 focus (1.6 tdci titanium).

I’ve noticed a fault on the trip computer, there are 4 values displayed (average mpg, average speed, current mpg and distance to fuel empty I believe). The current mpg is like a bingo machine, one minute it says 99mpg then 32.6mpg then 64.8mpg and so on, It just changes constantly. All the other values work fine.

Does anyone know why it would do this and/or how to fix it?

Many Thanks

[mjt]

It's not a fault. It's perfectly normal for the instantaneous mpg reading to fluctuate like this. It's because the load on the engine is constantly changing and the ECU is responding with constant adjustments to the fuelling.