With 100mpg, Ford’s C-MAX Energi plug-in hybrid is 5mpg more efficient than the Toyota Prius, according to the US Environmental Protection Agency (EPS). And it’s a point the company is keen to emphasise. It is also 2mpg better than the Chevrolet Volt.

Last year, the Prius took 54% of alternative powertrain sales in the US according to independent figures, with the rest of the sales divided between 10 other brands.

The problem facing all car makers is that more people consider a hybrid than actually buy one. Ford’s key point will be that the C-MAX has more power, space and efficiency than the Prius at a lower cost.

According to Reuters, Ford calls potential buyers "optimisers".

"They're looking for their dollar to go as far as possible and as smart a way as possible," Michael O'Brien, Ford's electrification marketing manager, told Reuters in an interview. "The notion of having MPGe (miles per gallon equivalent) that's best in class is a terrific advantage."

Ford's emphasis on improving fuel economy while lowering costs has got these ‘optimisers’ interested.

"Five years ago, the optimisers may not have even had us on their radar screen," O'Brien said.

Ford recently began selling the C-MAX hybrid and the Energi goes on sale later this year. A plug-in version of the Fusion midsize saloon [US version of the 2013 Mondeo] will go on sale in 2013. The C-MAX plug-in hybrid sells for nearly US$30,000 after a tax credit; the Prius plug-in is $32,000.

To boost efficiency, one design change from the European model is the addition of winglets to the rear corners of the C-MAX to improve aerodynamics, John Davis, chief engineer, said.