Popular hybrid vehicles like the Toyota Prius and Honda Civic Hybrid are lucky to get mileage figures above 50mpg (4.7L/100km) in real world tests, and in some cases are beaten by conventional diesel vehicles, but talk of next-generation hybrid models achieving up to 100mpg (2.35L/100km) are already rampart. Toyota revealed yesterday that its third-generation Prius will be launched next year and its first plug-in hybrid will arrive in 2010, but the carmaker also stressed that some of the mileage claims being spread are overly optimistic.

Speaking with Automotive News, Toyota technology expert Bill Reinert explains that the demands of real-world driving, such as rapid acceleration on freeways, can dramatically reduce the all-electric range of plug-ins. “Not everybody's going to get 100mpg," he said.

According to Reinert, the expected 40 mile all-electric driving range for future plug-in hybrid vehicles will suffice for most customers. However, he also warned that the technology may not live up to the hype and some customers may be disappointed, as was the case with the Prius, which was originally rated by Toyota as offering up to 60mpg (3.92L/100km) in city driving.