Current gasoline-powered hybrids can barely manage to keep ahead of small diesels in the mpg wars that will shape our future transportation structure, but in theory a diesel hybrid would rule the roost -- for the moment, at least. That's what Volvo will be showing off in Geneva shortly, promising a whopping 124MPG from the V60 plug-in diesel hybrid it announced a few weeks back. The car uses an internal combustion engine driving the front wheels and an electric one to spin the rears,
