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Technical Forum: How often should an oil filter be changed?

Counterman magazine presents 11 technical and sales topics in an easy-to-read question-and-answer format.


How often should an oil filter be changed?
 A.  As often as is necessary to keep the oil clean. The service interval can vary depending on the number of miles driven, the type of diving, the type of engine (gasoline or diesel), the mileage on the engine, the type of oil in the engine and the type of oil filter.


The goal is to change the oil before it undergoes viscosity breakdown, or develops harmful acids and sludge in the crankcase.

Short trip stop-and-go driving, especially during cold weather and especially in high-mileage engines with more blowby, causes condensation to build up rapidly in the crankcase.

If the car isn’t driven far enough or long enough to heat up the oil and drive off the accumulated moisture, sludge can start to form inside the engine.

Oil filters can remove solid particles, but they can’t remove acids or moisture from the oil. Consequently, if the oil and filter and not replaced, the engine can sludge up and possibly fail.


The general rule is to always change the oil filter when the oil is changed. The most common aftermarket recommendation is to change the oil and filter every 3,000 miles or every six months (if a vehicle is driven less than 3,000 miles during this period of time).

Vehicle manufacturers, on the other hand, are more liberal about oil changes.

Some recommend changing the oil and filter every 5,000 to 7,500 miles — or even longer. Some maintenance reminder lights may not come on until 10,000 to 15,000 miles! It should be noted, however, that many of these extended drain intervals are based on using high quality synthetic oil, not conventional motor oil. It should also be noted that some vehicle manufacturers have experienced engine sludging problems as a result of extending oil change intervals too far).
OEM filter replacement intervals are usually based on “ideal” operating conditions, which means mostly highway driving, trips that are at least 6 or more miles in duration, limited idling and not a lot of stop-and-go city driving, infrequent short trips (especially during cold weather), little or no driving on dusty gravel roads, and no trailer towing.


The OEM filter replacement intervals are also designed to minimize maintenance expense for the vehicle owner. That looks good on paper, but in the real world it can sometimes result in expensive engine wear and costly repairs.

Q.  What type of oil filter should I use?
A.  Many oil filter suppliers offer a range of filter types within their product lines. Typically, there is a “standard” replacement oil filter and an upgrade premium filter that offers extended service life, a finer filter media or both.
Premium grade filters typically include a higher efficiency and/or extended life filter media, and are often made with stronger tubes, end caps and canisters. The premium filter media helps keep the oil cleaner longer.


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