[Wolvreen]

Hi,
I have a 1.6 petrol i30 automatic.  It’s done 93k miles.  A few years ago my car changed from 36 mpg to 26 mpg.  The only thing I can think of is a faulty O2 sensor or dirty injectors.  Would these be flagged up on the OBD with alarms?

[eye30]

Is that mpg per the onboard read out or have you calculated by monitoring fuel refills, full tank to full tank?

[Wolvreen]

Calculating from refills.