Hi Ed!
British miles are the same as yours but our gallon is bigger than the US gallon (4.546 litres compared to 3.785)
Like you, we use a mix of Imperial and Metric measurements, all very confusing.
I still measure my fuel consumption in MPG and my diesel RAV is running at 44.1 MPG - mostly on rural roads, with some dual-carriageway (two lanes in each direction).
I have driven a lot of cars but The RAV is my first diesel and I am very pleased with it. European and Japanese diesels have improved enormously over the last few years. There is no black smoke from from the exhaust when starting from cold or when accelerating hard. The exhaust doesn't smell like a diesel, thanks to the catalytic converter I guess, but the fuel itself stinks and most filling stations provide plastic throwaway gloves.
At one time, the engine oil on diesels needed to be changed at pretty short intervals. On the RAV, oil changes are every 10000 miles with major services at 20000.
If gasoline prices escalate much more in the USA/Canada, I guess there will be greater demand for thrifty diesel vehicles.
John