Fuel mileage readings

[johners1949]

Hi everyone, haven't asked for any help for a while as everything seems ok, then lockdown happened.
    Before we weren't allowed out at all I filled the tank on our Stylance 140 bhp, and the mileage showed as
675 mls, which we usually see, but then we haven't been anywhere apart from a short run (2mls) to keep
some charge in the battery. I decided this wasn't worth the effort and now run the car for 5mins three times a
week, and use a battery charger. Since we can now use the car I find the full tank mileage has dropped to 420mls.
  Has anyone any ideas please, all suggestions gratefully received.
   AJohnson

[SirDavidAlhambra]

Hello Mr Johnson, how are u.

The car has detected that u have been getting bad fuel economy of late (because of all the idling and short journeys) and has accordingly revised its prediction of how far u will manage to go on that tank of fuel.

Fear not my nervous friend, the figure will go back up once u start driving normally again.

[johners1949]

Thank you very much for your reply, I was hoping it was something of that nature. I was hoping it was nothing
to do with the EGR valve, I had to replace that a few years ago and the scars haven't healed yet.!!!!