Energy tip #3: replace your car’s air filter

Replacing your air filter could help you save up to $150 a year…and allow you to afford your favorite coffee maker, a thermos, and finally drop those pesky disposable cups. It will also eliminate over 1,000 lbs of CO2 emissions.

The air filter (a slightly meatier version of the coffee variety) is a necessary part of your car that cleans particulates from the air before it hits your engine. The result is dramatically improved horsepower and efficiency. But drive around a while and the filter tends to collect grime, gradually diminishing its effectiveness. Just ask people who live in LA.

The Department of Energy claims that replacing a clogged filter can improve fuel efficiency by up to 10%. 10%? Smokes. That’s about thirty cents on every gallon of gas. Newer filters also sport improved designs. For example, you can find more environmentally friendly washable filters at autopart stores.

Let’s look at the math (spreadsheet here):

Miles/yr: 12,000
MPG: 19.6
MPG with clean filter: 21.56
Gallons saved per year: 56
$/yr. saved on gas: $165
Cost of air filter: $15-50

Total $ saved/year: $115-150
Lbs CO2 saved/year: 1,088

As always, you can add 12,000 lbs. of carbon reduction to your 1,088 by buying a Standard TerraPass — and you’ll still end up saving $65-100.

Last week about 30 people pledged to inflate their tires within two weeks.
30 x 383 lbs/person. = 11,490 lbs of CO2 reduced = 1 car off the road. Nice job everyone.

How many of you will be checking to see if you could use a new air filter?

Also be sure to check out Tip #1 and Tip #2 for other ways to finance a TerraPass or your morning bean brew.

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  1. Bill Wilson - July 19, 2006

    Changing the air filter is a great idea. The only reason I’m not doing it at the momoent is because mine is only about six months old. I think air filters should be changed every 12 months, if I’m not mistaken.
    And, in six months, I’ve driven the car less than 2000 miles, so my filter is still fairly young.
    Keep the great tips coming! I need to do the tire pressure thing this weekend.

  2. chris buchner - July 19, 2006

    Does anyone know an objective way to look at the filter and see if it needs to be changed?
    I cannot remember how long ago I changed mine.

  3. 1985 Gripen - July 19, 2006


    Hold it up to the light and see if you can see light through it. If you can, it’s probably okay. If you can’t, then it has to be replaced.

    However, the mere fact that you can’t remember how long ago you changed yours seems to indicate to me that you should go ahead and replace it.

    As for when to replace the filter, I think most manufacturers actually recommend replacement based on mileage rather than time. I just did the 60K mile maintenance on my car and one of the items on the checklist was to replace the air filter. You can usually find the maintenance schedule included with your car’s owner’s manual.

    As for the assertion that washable filters are more “environmentally friendly”: are you sure? You’ll be washing a lot of (I’m sure) toxic junk into the sewer system, using quite a bit of water to do so. Is this really better than a paper-based filter being buried at a dump? Furthermore, the leading vendor of re-useable air filters ( suggest you use their cleaning product ( when you clean the filters ( I highly doubt these are all-natural, biodegradable chemicals.

  4. JC - March 3, 2007

    First, look at the owners manual for when it should be changed. Usually by miles. Don’t go by what the auto dealer says. They want you to do it sooner, more often, and pay them the most to do it.

    Second, it also depends on where you drive. If you are in a dusty area/around farming, or in the city, the filter will have larger particles and be more clogged and clogged sooner.

    Thirdly, look at it and compare it to a clean filter that you have standing by. If it is dirty, grey, dark on both sides, it is probably time.

    Also, with a marker, write on the filter date installed and miles on odometer. I also write same on end of the filter box (with filter model number) so that I can use that to buy a new filter.

    If you have compressed air (as in shop air, not the canned kind) you can also blow out the filter and give it another few months of use. But ultimatly you want a clean filter more often in the car than a dirtly one.

    Be sure to wipe out the plastic box that the filter sits in under the hood with a shop rag.

    Don’t spend extra on a high end filter. If you are changing it properly, and it is a name brand or from a reputable automotive store, it will work fine!

  5. Joe - March 28, 2008

    Not only is it good for your gas milage,but replacing your air filter on a regular basis will increase the life of your car. If you don’t know how to replace it this helped me.

  6. Wallace Jacobs - July 2, 2008

    Replacing an air filter on a late model computer controlled car will have no affect on MPG. This is total bunk.