The Ford C-Max Energi, a plug-in hybrid, will be a milestone for many reasons. It will be the first plug-in hybrid from Ford, and it will also be the most spacious on the market. But there’s more as it will also be the most fuel-efficient, even better than the Prius v when used as a regular hybrid. Bonus is the ability to drive 20 miles on battery power. The fuel tank allows 530 miles of driving after that, giving a range of 550 miles. That sounds good at first, but the diesel Ford C-Max currently on sale in Europe has an even longer theoretical range: over 800 miles.

It’s so convenient, the average driver only has to go the pump one a month… But these are theoretical values calculated under different methods on each side of the Atlantic. Real world values may differ, but it’s a safe bet the diesel model will keep its lead. How about fitting a larger tank in the plug-in hybrid?