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Earth Sense: Fresh filters boost gas mileage, keep air cleaner
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If you’ve ever been stuck on a hilly North Georgia road behind a car blowing clouds of dark smoke, you may have wondered what’s wrong. In essence, the driver was using more costly gasoline than free air.

On uphill stretches, the exhaust fumes from such a vehicle can be unbearable. Of course, this is illegal as well.

An engine works like a big pump. It draws in air from the outside, mixes it with gasoline vapor and causes it to expand while burning very rapidly. The faster the air can move through the engine, the more power is available.

What the driver ahead of us neglected was maintenance of the car’s air intake. In most cases, it’s a black plastic box. Open it, usually without tools, and the air filter is accessible. The standard type is made of paper pleats. When dirt is present, it’s time to replace it because it is restricting air flow.

This is the simplest of car maintenance chores, and it brings back that “get-up-and-go” that was dwindling away.

A dirty air filter causes the engine to use more gasoline. It’s called a “rich condition,” which in this case isn’t a good thing. On our mountain roads, the problem becomes most noticeable.

The thinner mountain air makes the car or motorcycle run “rich,” with an accompanying loss of power and increased fuel consumption. Modern fuel injection systems compensate some, but they can’t make air available that won’t pass through the filter.

Older vehicles that still have a carburetor, including my old Harley, clearly start to breathe hard on the way up U.S. 441 in the Smoky Mountains and similar steep grades.

Changing the air filter is a task that anyone can accomplish without special automotive skills, and the filter costs only a few dollars. With a little extra work, you can even find a couple of additional horsepower by buying one of the red “lifetime” filters. The material there is cotton instead of paper, and requires periodic rinsing with soap and re-oiling.

Those high-flow devices pay for themselves in time.

The other advantage is that the filter material doesn’t swell up in wet weather like paper does. On rainy days, there isn’t that power loss that cars with paper filters experience. Whatever the choice, a clean air filter also helps keep our atmosphere cleaner.

Rudi Kiefer, Ph.D., is a professor of physical science and director of sustainability at Brenau University. His column appears Sundays and at gainesvilletimes.com.

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