Don't need to rev high if your diesel, the fuel isn't exactly as explosive as gasoline, but has more of a burn I guess ya could say.
But yea, Diesel is much easier on fuel these days if you have a WELL maintained light weight car compared to a gasoline version. The issue is, diesel costs a whole lot more. Some places here in the states it's a dollar or more per gallon than premium fuels. The sad part is, it used to be a bit less than the cheapest regular. xD