every 5 to 10 thousand miles
You should replace your furnace filter every 1-3 months, depending on the type of filter and how often you use your furnace.
One every month if you have allergies.
Check it at each oil change, and replace when dirty.
you should only need to replace your fuel filter about every 45-60k miles. Check your service manual for scheduled maintenance.
Per most manufacturers' instructions, you should replace your refrigerator's water filter at least once every six months. If your water tastes "off," you should consider replacing the filter even if it hasn't been six months.
Depending on how much you drive your car should be how often you change your air filter. Sources say you should change it when you go to get your oil changed cause they both last about the same time.
under the van, in the center.
Replace it every 36,000 miles.
If it has a replaceable filter replace it every 50,000 miles.
Your air filter should be changed each time you have a oil change or perhaps a tune up which should be every 6 months.
How often should you change the fuel filter?
If it is replaceable then replace it every 75,000 miles.