Dear Car Talk:
I have a 2014 Ford Focus with not quite 18,000 miles. It has the original air filter. The dealer says the air filter is fine and won't change it out, even when I told them to.
Should I do it on my own? Does the filter break down over time? Thanks. -- Lee
We're going to have to give this dealer a 15-yard penalty for refusing to sell you unnecessary parts, Lee. He's clearly trying to make the rest of us look bad.
Honestly, I can't remember seeing an air filter break down over time, Lee. The filter is made of pleated paper, surrounded by a rubber gasket. But it's fairly coarse paper. Put it this way -- it's not something you'd want to wipe your behind with, even in an emergency. It's not flimsy.
Air filters tend to get dirty way before they disintegrate -- barring intervention from a family of mice or something like that. It's even possible that when you've previously been in for service, someone removed your air filter and blew it out with compressed air -- removing any dirt and dust that it captured for you. So, is it possible for an air filter to still be good after eight years and 18,000 miles? Absolutely.
Changing or cleaning the air filter was much more important in the days of carburetors -- like pre-1980s. In those days, if your air filter was really dirty, it would reduce the air flow to the engine and mess up your fuel-air mixture. That'd make your car run poorly, harm your emissions equipment, and really reduce your mileage.
But with computer controlled, fuel-injected cars like yours, even if the air filter were dirty enough to limit your air flow, the computer would just adjust the fuel flow to match it. You might notice a little less power, but your mileage and emissions equipment would be unaffected.
So, if your dealer checked your air filter and says it's clean, there's no good reason to change it. On the other hand, we don't want you to lose any sleep over this, Lee. So, if it really bothers you, stop by the parts department and buy a filter for less than $20 and install it yourself. It'll take five minutes.
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