Over at Autoblog I read that The Economist has had a blinding flash of the obvious and discovered that a used Civic is less expensive than a new Prius.

But there’s more to the story: the author also found that changing the oil and air filter boosted the used Civic’s fuel economy from 34 to 40 mpg.

This set off my BS detector.

Changing the oil should have a negligible impact on fuel economy, and changing the air filter should be worth, at most, two to three mpg if the old one was fairly dirty. So while changing out a dirty filter is definitely a good idea, a six mpg gain shouldn’t be happening.

When my BS detector goes off, I check the methods that yielded the results. The 40 mpg figure appears to have been calculated legitimately enough, though the method isn’t stated. But the 34 mpg was calculated based on the following information, taken from the article: “The previous owners told me the car could get from Austin to New Orleans on a single tank of gas. That implied 34 miles to the gallon on highways and about 30 in the city.”

Wow, that’s quite a piece of evidence. First off, the previous owners didn’t say the gas tank was bone dry upon reaching the Crescent City. I’ll wager that it had a gallon or two left in it. And where did that “30 in the city” come from?

The Economist is a highly respected magazine. So how could they publish an article that makes claims based on flimsy evidence and faulty logic? The answer seems clear to me: they take cars no more seriously than they would Hollywood gossip.

Similarly, I encourage you to check the methods whenever a conclusion seems odd. Even a first-tier source like The Economist is not worthy of your blind trust.