For reference, the freaking big multi-ton Panzerkampfwagen I used to drive when I was in France gave me a neat 34 to 36 mpg on highways at those speeds. Same kind of engine - V6 diesel HDI - and better aerodynamics than the Espace.
Urban mileage was ugly though : 16 mpg or even worse (I don't dare remember, frankly). That where's an hybrid would help. But then, we Parisian scoundrels have this cool thing called public transportations like Le Metro and Le Tram, running on nuclear power. We also have feet. Very good for the waistline. Save for the rare run to the big box store or a drive to friends and family exiled in the suburbs, the Panzerkampfwagen always slept at the garage when I was in the city. Infinite mpg! Can't do better.
Example : the Chevy Volt which should be on the market late 2010 - early 2011. ~40 miles of full electric entirely on battery - with, very important, full speed/acceleration performances not a degraded mode like on classical hybrids with an electric-only mode - then very good mileage in gasoline mode beyond 40 miles of driving in a row.
