car’s mpg are not as manufacturer claim to be, moreso when it’s a big and heavy thing.
Verily in urban driving and also true for extraurban but only if you drive like a cock on the motorway or drive in the mountains. If, however, you cruise at a constant 65ish mph even big lumps can achieve those claimed mpgs because there´s no stopping and starting or pointless accelerating and braking cycles. We have a VW Caddy Maxi CNG (very heavy because of those gas bottles strapped underneath) and I regularly exceed the manufacturer´s extraurban mpg claim with shitloads of people and bikes and luggage inside. Ditto for a Focus diesel. Obviously results will improve drastically if you reduce cruise speed.
Also, I had no idea the Disco was so low nowadays. The boot in the news footage looked so tiny that I assumed it was an Evoque. What a pointless thing then. Where do one´s hunting hounds go?