The worst mpg that I achieved was in my first car, a 1974 Hillman Avenger, but it had a fuel leak, as I discovered once when I filled up with petrol in Exeter and it ran out before I got to Bristol which is just 80 miles away!
My privately owned BMW 520d was the best for fuel, averaging 47 mpg, even though I drove it ‘keenly’.
I don’t choose cars based on fuel consumption (I’d have an EV if I did) but for enjoyment (once all the practicality boxes are ticked). If they happen to return reasonable mpg then that’s a bonus, but it’s not a major consideration.
Our current Motability car (BMW X1) is exceeding expectations though. We certainly didn’t chose it for economy, but it averaged 44 mpg during the summer and is returning 40 mpg in the winter with the heater cranked up, heated seats on etc. I think that’s impressive for a quick 2.0i petrol auto with four-wheel drive. That’s better mpg than we were getting from our previous VW Tiguan diesel!