you know that the fuel consumption numbers calculated under ADR 81/01 have only a partial relation to real world values...
running a vehicle to determine fuel consumption is affected by many factors that are impossible to control and keep consistent (temperature, wind, loading of vehicle, driving style etc). The only way to get numbers that can be compared is to conduct the tests under laboratory conditions, so that the results are reproducable and consistent across all runs. In theory, if you drive your vehicle like they do in the ADR testing, you should get the exact same economy numbers.
see this link for more info:https://www.mynrma.com.au/cps/rde/xchg/ ... l-deal.htm
andhttp://forums.overlander.com.au/viewtop ... b95b945972
The numbers are indicative of fuel economy - they are good for comparisons between vehicles, but i don't think they make sense as absolute values - i.e trying to drive a vehicle around town and expecting the value on the sticker. these values should really be used as a guide, particularly when comparing vehicles.
some numbers that i typically get
2005 subaru outback H6,3.0L, auto ADR(combined): 11.1 typical usage (mainly around town): 12.8
2008 subaru impreza, 2.0L, manual ADR(combined): 8.8, typical usage (i drive 40kms door to door for work so certainly more country style driving): 7.6
2010 nissan pathfinder, 2.5TD, auto, ADR(combined):9.0, typical usage (mainly around town): 10.6
i hope that helps explain why you may not (ever) be able to match the fuel economy stated on the window