Writing about green cars can be a challenge. On the one hand, this site attracts many new-car buyers who want to learn more about more fuel-efficient alternatives to what they're driving now. Consider the Ford Explorer driver who bought a Honda Fit because it was really all he needed.

But on the other hand, it has a significant readership of green advocates who often seem to believe that driving anything other than the most fuel-efficient vehicle you can buy is a moral crime.

1979 Lincoln Town Car, Missoula, Montana

1979 Lincoln Town Car, Missoula, Montana

It's for them that we provide this gentle dose of reality, albeit with a needlessly provocative title. 

(1) Size and mass require more energy to move

In auto markets all over the world, drivers buy the largest vehicle they think they can afford to run. The bigger the vehicle, the heavier it is (despite all-aluminum luxury sedans like the Audi A8 and Jaguar XJ).The heavier it is, the more energy it takes to move.

Not everyone will drive the smallest vehicle they fit into. Nor should they, because ...

2005 Ford Excursion XLS

2005 Ford Excursion XLS

(2) Some families really DO need seven seats

There really are families with three, four, five, even six or more children. They need family vehicles. And that doesn't even get into the Little League coaches, the parents roped into carting athletic teams around, or just those play dates with multiple kids.

Families need bigger vehicles. Period. And a Mazda5 minivan, as admirable a vehicle as it is, just won't cut it.

(3) Some buyers tow very heavy things

Even ignoring work trucks, a remarkable number of Americans own fifth-wheel trailers, or haul motorcycles or ATVs or snowmobiles around on trailers, or tow 7,500-pound boats four hours each way to the lake house every other weekend.

2009 Dodge Ram 2500 ST

2009 Dodge Ram 2500 ST

Let's be clear: It's a way of life that's utterly alien to the rest of the world. But in parts of the U.S., the wherewithal to tow a large boat to a weekend house defines middle-class life. It means nothing to the average Chinese first-time car buyer--who provides the growth in global car markets--but as John Mellencamp sang, "Ain't that America?"

(4) There'll always be a low end of the scale

As fleet average gas mileage moves toward 34 mpg in 2016, there'll be cars that do better than that--battery electric vehicles that use no gasoline at all--and vehicles that do worse.

We'll still have seven- and eight-seat crossovers in 2016. While their fuel efficiency will likely be a lot higher than today's crop deliver (a 2011 Chevrolet Traverse AWD is rated at 16 mpg city, 23 mpg highway), they'll still be a lot lower than the compact sedans that deliver 40 mpg today, and probably better mileage yet by then.

Which will make those full-size crossovers gas guzzlers. Relatively.


2010 Chevrolet Suburban

2010 Chevrolet Suburban

(5) There'll always be a Texas

Texans really love their trucks. Big commercial-grade pickup trucks. Turbodiesel trucks. And Chevrolet Suburbans, which for many years sold half their production in Texas alone. Renting a compact car in Texas is an exercise in repeatedly losing your vehicle because you can't see it among the parked trucks.

Yes, Texans (and many other Americans) drive long distances. But not every Texan needs a truck to go from a gated suburban community to the nearest mini-mall or high school. Perhaps it's the state's history as the former source of much of this nation's crude oil.

We hope it's not a representative sample, but more Texans have sneered to us at the idea of using less gasoline than residents of any other state. You almost get the sense that Texans take a perverse pride in using as much gasoline as possible. It's some kind of cultural indicator of manhood or something, except that Texan women drive pickups too.

Texas Governor Rick Perry may be the only one of 50 governors to call out the Toyota Prius hybrid by name just to sneer at it. (He was wrong; it holds five bales of hay.) He also accused the EPA of "preparing to undo decades of progress" and "destroying hundreds of thousands of jobs."

Paradoxically, Texas also produces lots of renewable energy, and would benefit from natural-gas vehicles, given regional supplies. But we suspect Texans will consume more gasoline per mile driven long after mileage standards tighten.

(We welcome Texans to weigh in with opposing viewpoints, by the way. Please leave them in the Comments below.)