Mileage and power

I've used a Hypertech device to play with the map on my car.

It gives the car a little more power, but the side effect is that I have better fuel economy.

It's an odd reading as it measures in litres per 100 miles, rather than the traditional miles per (imperial) gallon.

It's gone from 17.6 litres per 100 metres to 16.2. This means it's gone from 25.8 to 28mpg!