Photo from Hugo90 on Flickr.

About a year ago I was at a conference where the keynote speaker dispensed the conventional wisdom that buying a used car is more environmentally friendly than buying a new one, even something like a hybrid.

Seems like a no-brainer, right?  Manufacturing a new car requires enormous mining, manufacturing, transportation and other costs and energy inputs, while a used car doesn’t need to be manufactured; it already is.

You can find articles agreeing in Wired, Knol, Scientific American, BrakeandFrontEnd Blog and many other places.

If you are worried only about your own personal environmental footprint, then the used car is likely better.  But if you are concerned about the entire planet, you have to draw a larger circle than just around yourself, and that changes the answer.

When one goes to purchase their replacement vehicle, what happens to the one they already have? In most cases it is sold to someone else, who eventually sells it to someone else until it finally completely dies after about 17 years and several owners. 

In fact, every car that is manufactured will be on the road until it finally is totaled or gives up the ghost.  Your particular ownership of that car is just a waypoint on the path from manufacturer to junkyard.

A better outcome, from an environmentalist’s standpoint,  is for manufacturers to start churning out more and more high mileage and hybrid cars and working desperately to design and build the next, even better generation of vehicles.

The way to get the manufacturers on board is to affect demand. Car builders claim over and over that they manufacture to meet the demand of buyers — it’s why GM claimed it was building so many SUVs, for instance.

Manufacturers don’t care about used-car buyers, even if demand for used cars sends a weak signal. If I buy a new, cutting edge, fuel-efficient vehicle, then I’m sending a signal to the manufacturer to make more of those.  If I buy a used car, I’m not sending any signal, but someone buying a gas-guzzler might be.

Buying a used car neither reduces the total number of manufactured cars nor the number of cars going to the junkyard: remember, each owner is just a way station along the car’s trip.

Another way to look at the argument is to scale it up.  Thought experiment: a fleet buyer is buying 100,000 vehicles. Imagine the difference between placing an order for 100,000 new hybrids vs. buying 100,000 used cars.  Which is going to make the manufacturers sit up and take notice — and maybe even invest in new factories? 

In fact, what if that fleet owner put in an order for 100,000 every year? There’s an interesting twist.  Counterintuitively, by making that argument writ small we learn that buying a new efficient car every year is better than buying one and making it last.  And it’s true (although not practical for most people).  It would send an even stronger economic signal to manufacturers.

In the end, the decision about replacing your car includes a lot of factors, not the least of which is your own personal financial situation.  But if you’re thinking about a new car, but have considered a used car for environmental reasons, think again.

Incidentally, Slate did a comparison that also comes out in favor of the new Prius even without invoking my macroeconomic and macro-environmental arguments.

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Steve Offutt has been working at the confluence of business and environment for almost 20 years, with experience in climate change solutions, green building, business-government partnerships, transportation demand management, and more. He lives in Arlington with his wife and two children and is a cyclist, pedestrian, transit rider and driver.