Peter what usage are you doing? Are you driving in a conservative fuel saving way? My Forester gets between 8 and 8.5L/100 kms, which ain't too bad (older 2L). Is it worth the extra effort and conversion expense?
Nah. Some of these 4wd's I see people talking about are more fuel efficient than large aussie made sedans....
I agree oil will have to go much much higher before anything really changes. Some minor things like carpooling might happen earlier though.