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Ask Mr. Green: Hybrid or Natural-Gas Car?

Posted Mar 07 2013 8:23pm

Mr. Green is Bob Schildgen Hey Mr. Green,

My husband claims that hybrids are greener than natural-gas-powered cars. What’s your take on this?  

—Naomi, in Berkeley, California

I’ve noticed that male declarations about vehicles are often not just wrong, but off by an order of chest-beating magnitude, but your hubby’s on target here. The hybrid is the clear winner because of its greater efficiency, as you can see by comparing the two types of Honda Civic. The natural-gas-powered Civic gets a fuel economy of the equivalent 31 miles of gasoline per gallon in combined city and highway driving, while producing 227 grams of greenhouse gas emissions per mile. By contrast, the hybrid Civic’s combined mileage is 44 mpg, with lower emissions of 202 grams per mile, according to the EPA. They are tied in EPA’s smog score, with an excellent 9. In terms of sheer energy consumption, the natural-gas Civic uses around 4,000 British thermal units (Btus) per mile, whereas the hybrid requires only about 2,820.

The Prius C hybrid, which won the 2013 greenest car of the year honors from the estimable American Council for an Energy Efficient Economy , beats them all, with a combined fuel efficiency of 50 mpg, while requiring 2,480 Btus per mile, and producing 179 grams per mile of greenhouse gas emissions. It scores just a notch lower on the smog index, garnering an 8.

Of course there will be variations in these numbers depending on what how much driving you do in town and how much on the highway. The EPA derives its estimates based on the assumption that 45 percent of your driving in on the highway, and 55 percent is in the city. The natural-gas Civic drops to 27 mpg in town, whereas it goes 38 on the road. Hybrids tend to do better in the city because their braking generates power for the electric motor. The Prius is rated at 53 mpg for in-town driving, but drops to 46 mpg on the highway. But even if all your driving is on the highway, the hybrid will still beat the natural-gas model. (For details see www.fueleconomy.gov ).

I hasten to add that these numbers will be way, way off for a lousy driver who speeds, does jackrabbit starts and stops, sits around pointlessly idling the engine while waiting for a burger or a kid, fails to keep tires fully inflated, carries around a lot of extra weight in the car, uses the wrong oil, and just plain doesn’t maintain the damn thing. It’s been estimated that up to 45 percent of car’s fuel, whatever kind it uses, could literally be going up in smoke because of its owner’s lame driving habits and general negligence.

Got a question?  Ask Mr. Green !


READ MORE:

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Ask Mr. Green: Are Plastic Food Containers Too Toxic to Reuse?

Ask Mr. Green: Can I Build a Backyard Wind Turbine?


Bonus: Sierra magazine's EV buyer's guide


 --illustration by Little Friends of Printmaking

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