Over in the UK, the Telegraph has had a chance to spend some time with the new Ford Fiesta ecoNetic and came away with the realization that as mileage goes up you pay an increasingly high price for smaller and smaller returns. The problem, as we've mentioned here before, is the inverse relationship between mileage and fuel consumption. Each time you double the miles per gallon, the number of gallons used is cut in half. As the consumption gets smaller, those halves also become increasingly small. The chart after the jump shows the relationship between mileage, consumption and savings. It becomes pretty apparent that beyond 40 mpg, the actual savings start to become vanishingly small, while the cost of those savings get ever larger. Case in point is the Fiesta ecoNetic. A base Fiesta starts in England at £8,695 while the 1.4L diesel goes for £10,795 and the ecoNetic runs £11,845. That's £1,050 to go from 56 mpg (U.S.) to 63.5 mpg (U.S.). That 7.5 mpg improvement will net you a savings of £71 in fuel costs over 8,000 miles of annual driving. The car itself is definitely pretty nice and if people can actually get car loans again in 2010, Ford will probably do well with the Fiesta. However, not having access to the ecoNetic version may not be such a bad thing.