Well this weekend I drove 500km (90% of it was 110+ speeds) and I managed to get 12.2 l/100km (19.44 mpg US, 23 mpg UK)
I have achieved 10.5 l/100km (26mpg UK) using cruise control the whole way and not going over 110 km.
My regular drive back and forth from the Uni really guzzles gas. I never go more than 60km, and its all stop and go. The distance is only around 6km one way.
I am sometimes impressed with the highway milage, but its rare to drive 2hrs straight with cruise control on a single speed.
I am not sure if the conversions are correct I used this:
http://www.markporthouse.net/rangie/...onversion.htm#