Originally Posted by vnx205

I was just trying to make the maths simple by using 100%.
By the way a 100% improvement on 28 mpg is 56 mpg, (not 14 mpg as you state)
I would have though that it was more important to know the actual change in consumption rather than the percentage. After all as you point out yourself, it depends on what it is a percentage of. That was one of the points I was trying to make.