dont think i have ever owned a car that has done the mpg the makers lie about from past experience, if mpg is the important bit which travelling 80 miles per day i would think would be as if car will do barely 40mpg your looking two gallons per 80 miles,, but at motorway speeds you prob will struggle to hit mid 30s in the real world. ie add add road conditions and wind and hot and cold temps all have a impact.
me and wife would play mileage game see how many miles could get we found on all cars the magic road speed and mileages were on a motorway just below 50mph which is not very realistic, even then struggle to get what the makers figures were, the clubman cooper d was the only one we had that was close to it, we had that mapped 160bhp and it went as good as any standard cooper s petrol engine, while still giving over 70mpg on the flat driven at 50mph,, if buying a new unused mini diesel with makers warranty and keeping for 5 years max there good safe bet, if secondhand and is a n47 diesel over 70k on the clock should only buy one if timing chain and dpf filter has been replaced..
or the 3rd way new mini phev think you get best of both worlds, in a perfect world a phev connected to a house that has solar panels on it will help off set changing costs, and also future proof,, face it no one knows what this idiot governments are going to do next in the name of hit the car owners.
or could do a lease agreement just add fuel get a new car every year or so and just have a fixed monthly cost for the car,, doing big mileages i would say its a good option as long as the mileage clause is not silly low