First, reset your average meter reading by pressing the knob to actually know the current average.
Second, calculate your average manually on full tank (most reliable method). You can simply do this by following below steps.
- Reset trip A reading by pressing the knob for few seconds.
- Ask the guy at petrol pump to fill tank up to maximum but stop when nozzle lever release on its own (auto stop). Note down the petrol quantity in litres. For example your car got 23.5 litres of petrol.
- Drive your car as per routine.
- When reserve light blinks, note down the the reading on trip A. For example your car did 410 Kms.
- Now, simply divide 410 by 23.5 to know the actual average of your car. In this case it is 17.44 km/l
- Repeat above steps on next fill-up to have a confirm idea about your car average.
I hope it helps.