General Motors isn’t at all that happy with the latest 2011 ratings from the Green Car Book, which judges the new models on a point scale that includes not only fuel economy and tailpipe emissions, but also such relatively arcane measures as factory pollution and ease of recycling.

The Volt was far below the Nissan Leaf (second place), the Smart fortwo (third place) and even such conventional gas burners as the Mini Cooper (10th place) and the Hyundai Elantra (ninth).

The Volt was in 12th place, at the bottom of the list. And it didn't appear at all in the separate "Greener Choices" ranking, which lists the best cars in various categories. The Leaf got a green score of 54, the Volt 48.

The Volt did relatively poorly because its fuel economy with the engine running isn’t anything to write home about, just 35 mpg city/40 highway. GM would argue that it’s irrelevant, and it has a point — the major consideration is overall economy, which it once cited as 230 mpg (but then abandoned that figure). Many Volt owners will hardly ever use the gas engine, and it rarely kicked in during my four days with the car this month.

“Their logic would escape the majority of consumers,” said Rob Peterson, a General Motors spokesman. “If you look at the EPA ratings for the Smart fortwo at 33 city and 41 highway, it’s actually less than the Volt’s after the electric range is exhausted. We’re being penalized against the Smart because our car is a four-seater with a battery pack and therefore weighs more. And we lose against the Leaf because we have a gas engine. But you really have to look at how the car is actually used — their methodology doesn’t add up.”

The plain fact is there’s no universally accepted means of judging plug-in hybrid fuel economy. No other car has such a schizophrenic profile — zero emission half the time, a tailpipe emitter the other half. The Volt is a game changer, so it has to change green measurements, too.

The Green Book, produced by the American Council for an Energy-Efficient Economy (ACEEE), says that in evaluating plug-in hybrids, it considers both the emissions from the gas engine and from the power plants that feed the grid. But, of course, grid emissions vary widely, and the Volt would be much cleaner in California than in, say, coal-heavy Indiana. But the grid is becoming cleaner, with coal down from 56 percent of the national mix to 45 percent in 2009.

The Smart fortwo hasn’t been able to cash in on its routine high green scores, which are also elevated because of the car’s recyclable plastic body panels. Polls put fuel economy as the number one buyer priority in 2011, GM says, but consumers also want some things the Smart hasn’t provided, including performance and comfort. And few people bought the number one green car, the Honda Civic GX, which burns natural gas. The stations are scarce, among other factors.

It will be interesting to see how The Green Book does with such future cars as the plug-in hybrid Toyota Prius and the Fisker Karma. By the way, the Green Book also rates the “meanest” vehicles for the environment, and the absolute worst is the Ford Expedition/Lincoln Navigator pair (13/18 mpg). This year the list was short on supercars — no Ferraris! But the Bugatti Veyron placed on the baddie list, as did two Bentleys.

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