Filters are the engine and transmission's only defense against solid contaminants and premature wear. The oil filter traps solid contaminants in the oil such as dirt, carbon and metal particles so they don't damage bearing, journal and cylinder wall surfaces inside the engine. The transmission filter's job is the same, to prevent wear particles and dirt from reaching critical parts inside the transmission.
Changing filters regularly can significantly extend the life of the engine and transmission. Yet, study after study shows motorists are neglecting basic maintenance and are suffering the consequences as a result. The engine and transmission are the two most expensive components in a vehicle. Replacing an engine may cost upwards of $3,000 or more, and $1,500 or more for a transmission. That's why it makes sense to protect these components with regular fluid and filter changes.
Filters have to be replaced periodically because the contaminants they trap continue to build up until the filter becomes plugged. At the very least, motorists should follow the recommended replacement intervals in their vehicle owner's manual. But that means reading the fine print. In many cases, vehicle owners should follow the "severe service" schedule rather than the "normal service" schedule because of the type of driving they do. Short trip, stop-and-go driving, especially during cold weather, requires more frequent oil changes.
For the best protection, recommend changing the motor oil and filter every 3,000 miles or six months.
Transmission FilterAs for transmission filters, many transmission experts recommend changing the fluid and filter every two to three years or 30,000 miles or once a year or every 15,000 miles if a vehicle is used for towing or other severe service use.
The transmission filter is probably the most neglected filter on today's vehicles because of its location. To make matters worse, some vehicle manufacturers fail to list a recommended replacement interval for transmission fluid or the filter in their owner's manuals.
Automatic Transmission Fluid (ATF) doesn't build up acids and sludge like motor oil because there are no crankcase blow-by gases to contaminate the fluid with moisture. The only contaminants are friction materials from the clutch plates and metallic particles from normal gear and bearing wear. The filter will trap most of this debris before it can cause problems. But most Asian transmissions, as well as some older domestic transmissions, only have a plastic or metal screen that does little to protect the transmission against internal contaminants. It stops the big chunks, but that is all. It does nothing to keep the fluid clean. On these applications, changing the fluid is the only way to get rid of unwanted contaminants.
Changing the transmission filter requires dropping the transmission pan, which also requires replacing the pan gasket. Identifying the transmission application may require more than the year, make and model. You may also need the engine size as well as the transmission type. Many transmissions are identified by the shape of the pan gasket and/or an OEM ID number on a plate attached to the transmission or transaxle. If you are not sure about an application, you can always compare the old pan gasket to the new to see if they match. The same rule-of-thumb applies when changing the filter.
When changing the transmission filter, it will usually take four to 10 or more quarts of ATF to refill the transmission. Be sure to use an ATF that meets the vehicle manufacturer's specifications. Using the wrong type of ATF can cause shudder and shifting problems, and increase the risk of transmission failure!
Air Filter
Use a bright shop light to inspect the air filter.Air filters keep dirt out of the engine that can cause wear in the cylinders and bearings. The factory recommended replacement interval for air filters on some engines might be as high as 30,000 to 50,000 miles. But the life the filter varies so much depending on environmental conditions that most experts recommend checking the filter when the oil is changed and replacing it yearly.
To inspect the air filter, open the air filter housing (which is held shut with clips or fasteners), remove the filter and hold it up to a bright light. If the filter is very dark and transmits little light, it is dirty and needs to be replaced.
The life of an air filter can be extended by tapping the filter against a hard surface to knock dust loose, or by vacuuming the side that stops the incoming dust. Do NOT attempt to wash a dry paper filter element as this may damage the filter.
A word of caution about aftermarket low restriction cotton air filters (K & N brand, for example). The cotton filter element is less restrictive than a typical paper filter element, so people sometimes install these type of filters to improve airflow and horsepower. But to get dirt to stick to the filter, the cotton filter element is sprayed with a light coating of oil. On engines with a mass airflow (MAF) sensor, this can sometimes cause problems if some of the oil is drawn into the airflow sensor. The oil will contaminate the sensor, causing it to under-read airflow, resulting in performance problems and a possible Check Engine Light. The cotton filter elements are washable, and must be re-oiled after washing. So use oil very sparingly when you re-oil the filter if your engine has a mass airflow sensor.
Cabin Air FilterOn newer vehicles, cabin air filters also need to be inspected and replaced regularly. Cabin air filters keep odors and microscopic airborne particles out of the passenger compartment, so they are more of a comfort item than a performance item. Even so, a plugged filter can reduce airflow into the HVAC system, which may restrict airflow through the air conditioner or heater.
Cabin air filters have been used on some import vehicles as far back as 1994, and are currently installed on about 40 percent of all new vehicles (mostly luxury models). Many of these filters use activated carbon so they have a limited life. Replacement recommendations vary, but are typically 12,000 to 15,000 miles, or once a year. For dust-only filters that do not trap odors, the recommended replacement interval is typically every 2 to 3 years, but more often changed may be needed if the vehicle is driven frequently in dusty conditions.
The cabin air filter is typically located under the dash or behind the glove box, but some are under the hood at the base of the windshield. Refer to your owners manual for the exact location. Also, some cars (late model Fords primarily) have a place for a cabin air filter, but were not factory-equipped with a filter. Even so, a filter can be installed in the slot to provide cabin filtration.
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