Earlier today, GM officially unveiled the Chevy Volt, a sporty sedan which will reportedly get 40 miles on a single battery charge. (Read our full report here.) The car, expected to be priced just under $40,000, will start production either late this year, or early in 2011. According to GM, the Volt will get city fuel economy of at least 230 miles-per-gallon, and come packaged with a flex fuel-powered engine-generator.

Sounds pretty good. But at least one competing automaker isn't convinced. "Nissan Leaf = 367 mpg, no tailpipe, and no gas required. Oh yeah, and it'll be affordable too," the folks over at Nissan's electric vehicle Twitter feed wrote today. About an hour later, they added this statement: "To clarify our previous tweet, the DOE formula estimates 367mpg for Nissan LEAF."

Team Nissan is referring, of course, to the electric vehicle in the photograph above (and the video below). The LEAF, which will go into production next year – with a tentative release date of 2012 – is expected to be much cheaper than the Volt. How much cheaper? Nissan isn't saying. Wired, for one, thinks the cute-as-a-button car could come in at $25,000 – some $15K cheaper than the Volt.

But more important: Is Nissan right when it claims the LEAF will have a better MPG than the Volt? Yes and no. As Daily Tech points out, it's all a numbers game:

Nissan boasts of the higher mpg rating because its LEAF features a 24 kWh lithium-ion battery, while the Volt makes do with a 16 kWh lithium-ion battery. This gives the LEAF a battery-only range of 100 miles compared to just 40 miles for the Volt. However, the Volt has the advantage of being able to rely on its generator to travel an additional 300 miles – something that Nissan cannot say about its LEAF EV.

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You tell us: Volt or LEAF? Or neither? Sound off in the comments section, or on Twitter.