Top five cleanest gasoline cars

Four of the five pollute less than some hybrids

With all the attention the emerging technologies are getting in the automotive press, you tend to forget about the decades-old standard, the conventional gasoline engine.

You're definitely paying a premium to be green, with hybrid technology easily adding two or three thousand dollars to the price of a car. And most electrics, such as Tesla's roadster, are priced only for the wealthy. Makes for great red carpet press for the Hollywood-types but the everyday, commute-to-work driver, just can't afford it. Even GM's Volt will be priced in the $40,000 range, before any government subsidies kick in.

So rather than concentrate so much on the new, NADA Guides has released a list of the top five cleanest conventional gasoline cars for this year's Earth Day.

"It is no surprise that on Earth Day the automotive world will be focused on the latest and greatest hybrid vehicles, but the fact remains that consumers are still overwhelmingly buying and driving conventional gasoline cars," said Michael Caudill, spokesperson for NADA Guides. "The Top Five Cleanest Conventional Cars show that consumers have options for vehicles that are easy on the environment without the higher price point of emerging hybrid technology."

The cars that made the list were based on a combination of scores from three criteria: greenhouse gas emissions, smog-producing air pollution and combined miles per gallon. All data was based on 15,000 miles of driving per year, with 55 percent of it city driving and 45 percent highway driving.

Greenhouse gas emissions include carbon dioxide, methane gas, nitrous oxide and hydrofluorocarbons. Theses figures are expressed in tons per year. Smog or air pollution includes nitrogen oxides, carbon monoxide, various carbon-containing compounds (including hydrocarbons), formaldehyde and solid particulates.

It's nice to see three of cleanest cars are from American manufacturers; i.e., the 2009 Pontiac G5, the 2009 Chevy Cobalt LS and the Ford Focus S. The Hyundai Elantra GLS lands up in the middle of the pack with the 2009 MINI Cooper coming in last. It's surprising to see the MINI as the dirtiest of the bunch, with it emitting the most air pollution yet still being very efficient. You can bet BMW will work to clean it up.

As many would argue, hybrid and electric technology is not ready to replace the traditional gasoline engine. Will prices adjust eventually? Probably. But until then, you have a few options to be green without paying for it.