As cars get more reliable and last longer, the case for buying "gently used" cars gets stronger and stronger.

But suppose you want to drive green, and you're aware that the newest cars get the best gas mileage.

What used cars can you buy that will let you drive green and deliver the highest fuel efficiency?

This piece is the introduction to a list of five cars we'll feature--one per day--over the coming week.

They're our picks for five ways to buy the greenest cars from U.S. used-car lots.

As always, carefully check over any used car, and consider whether the reassurance of a certified used car from a dealer outweighs the higher prices those carefully-checked vehicles command.

2009 Toyota Prius

2009 Toyota Prius

(1) 2004-2009 Toyota Prius: 46 MPG

The second generation of the quintessential hybrid car, the one that America thinks of when it thinks of "good gas mileage" (and perhaps "annoying progressive green types"?), is by far the most plentiful green car at used-car dealers.

Their owners tend to hang onto them and rack up lots of miles, however, so you may have to do some hunting to find a low-mileage used Prius.

Still, if you want a combined EPA rating of 46 mpg in a five-door hatchback that's classified as a mid-size car by interior space, this is your only option.

(2) 2006-2011 Honda Civic Hybrid: 41 MPG

Honda just launched its third generation of the Civic Hybrid for 2012, but we're suggesting the second generation as a good used buy. It's EPA-rated at 41 mpg combined.

There have been some issues with recalls around battery life, so proceed with caution.

But our driving experiences with the second-generation Civic Hybrid were, perversely, more than enjoyable than those with the latest edition.

And unlike the Prius, no one will know you're driving a hybrid if you get the hybrid Civic--only Honda fanatics can tell the difference between it and the garden-variety versions of Honda's compact four-door sedan.

2009 Volkswagen Jetta TDI

2009 Volkswagen Jetta TDI

(3) Volkswagen Jetta TDI: 34 MPG

Volkswagen diesels have diehard fans, and the Jetta TDI has long been VW's best-selling diesel vehicle in the U.S.

It vanished from the market in 2007 and 2008 due to stiffer emissions requirements, but it returned for 2009 and is the mainstay of an expanding lineup of VW diesels from the Golf hatchback to the big, expensive Touareg sport utility vehicle.

Diesel Jettas are widely acknowledged to exceed their EPA ratings (34 mpg combined for 2010), and if you cover a lot of highway miles, this may well be more fuel-efficient than a similarly sized hybrid--and it's absolutely more fun to drive.

(4) 2004-2011 Ford Escape Hybrid: 29 MPG

Long a favorite of ours, and of eco-conscious suburban moms everywhere, the Escape Hybrid has steadily improved over the years.

Through two restylings and many upgrades to its control software--plus the addition of electric air-conditioning for 2010--the hybrid Escape delivers compact crossover utility and a combined EPA rating of 29 mpg (for 2011) in either front-wheel or all-wheel drive models.

And their batteries last too: Many Ford Escape Hybrid taxis have logged 300,000 miles or more.

2009 Chevrolet Tahoe Hybrid

2009 Chevrolet Tahoe Hybrid

(5) 2008-2011 Chevrolet Tahoe Hybrid: 21 MPG

OK, OK, stop howling. Yes, some people really DO need the size, capacity, and brute-force strength of a full-size truck-based sport utility vehicle.

For those people, the hybrid version of the Chevy Tahoe is by far the greenest choice on the market. They don't sell many--a few thousand a year--but we've tested the big hybrid SUV, and it does a superb job.

If, that is, you really do need a full-size SUV. They can be hard to park, they have all the aerodynamic grace of a small municipal hospital, and no one will know you're driving green.

But if you really do need a big SUV, this is the greenest one, at a combined EPA rating of 21 mpg (for 2011)--versus just 17 mpg for the best standard model.


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