[cleanspeed1]

Yes, yes, yes! At least for right now. If you look at the new gasoline/direct injected engines, it's all diesel technology using a different fuel and a spark. Mazda's Sky Activ ( gas version ) uses 14 to 1 compression, direct injection and other jiggery pokery to do the deed.

Part of it is the high compression ratio, the other part is the energy density of the fuel. Diesel fuel has more energy per gallon than gasoline. The cam timing usually trends toward making maximum torque at low engine speeds, so you don't have to rev it as high.
So the combination of all these elements yields a high mpg device.