Just picked my scooby up from the dealers after its first 1k service. Driving home the gauge went from just under half full to empty in about 20 miles! (I did have the aircon on but )

When I filled her up she only took £30 instead of the normal £46-48. After that she only showed 1/4 full

After the football I took her on a longer blast down some dual carriage ways and opened her up a bit. After a few minutes the gauge went up to full and she has been alright since......


What would cause this ? anything to worry about ?
just concerned because she had her service today........

 

bouncey bouncey !!

I know its boring but I am curious and always willing to learn


I've done a search and someone else has had the same problem but they didn't get any response either !!