The feds, eager to make fuel economy stickers easier to understand even as new technologies enter the market, suggest assigning all new vehicles a letter grade based upon their efficiency. The best fuel misers would, as you'd expect, get an A while the worst guzzlers would get a D.

Assigning each new car an overall grade based on fuel economy and greenhouse gas emissions would the biggest change to vehicle window stickers in 30 years. The proposal is one of two the Environmental Protection Agency and Department of Transportation are considering under a sweeping effort to revamp vehicle window stickers for the 2012 model year. That's when electric vehicles and plug-in hybrids are expected to hit the market in (relatively) significant numbers.

Current stickers provide each vehicle's fuel economy in miles per gallon and an estimate of its annual operating costs. Under one proposal, the feds would add a letter grade summing up a vehicle's energy efficiency and greenhouse gas emissions. Under the second, current stickers would be updated to include comparison of various vehicles' fuel economy and emissions.

The goal is to provide consumers with a simple, straightforward way to compare the energy consumption and environmental impacts of all types of vehicles, from internal combustion vehicles to electric and plug-in hybrid. Regulators want some public feedback before deciding which proposal to adopt.

“New technologies such as battery electric vehicles and plug-in hybrids are entering the American market in greater numbers,” Transportation Secretary Ray LaHood said in a statement. “We need to provide consumers with labels that include fuel economy and environmental information so that buyers can make better informed decisions when purchasing new vehicles.”

The grades would range from an A+ to a D, perhaps to spare automakers from having to see their least efficient vehicles slapped with an F. To earn top marks, a vehicle would have to get at least 59 mpg or the equivalent, while anything getting 14 or below would earn a D.

Clearly some vehicles will blow the curve. An electric vehicle like the Nissan Leaf would get an A+, while a plug-in hybrid like Toyota's forthcoming Plug-In Prius would earn an A. The average car like, the Toyota Camry, for example, would score a B-, while most SUVs and pickup trucks like the Ford F-150 would fare no better than a C+. Extreme performance machines like the Ferrari 512 Scaglietti would get a D.

A second proposed label would retain the current label's focus on miles per gallon and annual fuel costs but update the overall design and add comparison information on fuel economy and emissions.

Automakers are, as you might expect, skeptical of the proposed changes.

"A car is generally a consumer's second biggest expenditure, and automakers support providing our customers with meaningful information for decision-making on vehicles that meet their particular needs, but the proposed letter grade falls short because it is imbued with school-yard memories of passing and failing," Dave McCurdy, president and CEO of the Alliance of Automobile Manufacturers, told the Detroit News. The trade association represents the Big Three, Toyota Motor Corp., and seven other companies.

Automakers also worry letter grades amount to the government making a value judgment on vehicles.

"Grades may inadvertently suggest a government label of approval, when what we really want to do is encourage consumers to consider buying one of the many new technologies on sale," Gloria Bergquist, spokeswoman for the Alliance of Automobile Manufacturers, told the Wall Street Journal. The alliance is the auto industry's largest trade group.

Both labels expand on the data currently available by providing new info about fuel consumption, tailpipe CO2 emissions and smog-related emissions. The new labels would provide information on a web-based interactive tool also accessible by smart phone.

When it comes to electric vehicles and plug-in hybrids, the feds propose showing energy use by translating electricity consumption to miles per gallon equivalent, but the labels also would express energy use in terms of kilowatt-hours per 100 miles. GHG emissions would be measured only at the tailpipe and would not consider any "upstream" emissions from, say, electricity generation. That's sure to be a bone of contention among EV naysayers who argue electric vehicles simply transfer emissions from the tailpipe to the power plant, even though some studies have shown the well-to-wheel emissions of electric vehicles are lower than internal combustion even when the electricity comes form coal-fired plants.

The feds will take public comment for 60 days after the proposal is published in the federal register, so click here if you want to sound off.

Photo: Ford. A dealership employee prepares a Ford Escape Hybrid for delivery. Under the feds' proposed window sticker revisions, customers shopping for cars would more easily be able to compare different vehicles' fuel efficiency and emissions.

Under one proposal, the feds would assign all new cars a letter grade based upon energy efficiency and tailpipe emissions. The label also would outline projected annual savings in fuel costs over the average vehicle. Electric vehicles would get an A+, while plug-in hybrids would get an A.

The most fuel efficient gasoline cars would earn high marks, and most SUVs would get a C+. Anything getting 14 mpg or less would earn a D. Just like so many schools these days, no one would get an F.

A second proposal calls for updating the current stickers. Electric vehicles would show energy use by translating electricity consumption to miles per gallon equivalent, but the labels also would express energy use in terms of kilowatt-hours per 100 miles.

The feds say the redesign is meant to make it easier for consumers to compare the fuel efficiency of various vehicles and technologies.