Initially,early automotive engine designs didn’t use any oil filtration. That wasokay in the days when oil was dumped every 500 to 1,000 miles, or ifthe engine burned or leaked enough oil during normal operation thatalmost constant replenishment with new oil compensated for anyaccumulated dirt.
We’ve come a long way. Not only are allvehicles designed with an oil filter, the filter media is now made ofcellulose, fibrous materials or synthetic materials designed especiallyfor this purpose. Materials in an engine’s primary filters today pullout particles as small as 25 microns (a human hair is 67 microns indiameter).
Primary oil filters are standard on most engines.They are also called full-flow because 100% of the engine oil passesthrough them in normal operation. The filters must work withoutintroducing a lot of restriction, or else oil will not flow in theengine during cold start-ups. This is one reason a full-flow filterallows the passage of comparatively small contaminants; to try andcatch everything would restrict flow.
If blockage occurs in thefilter, bypass valves open. This allows oil to go around the filter andback to the engine. In this situation, lubrication with unfiltered oilis better than none at all.
We’ve even gotten to the point ofusing filter magnets. The route that engine oil takes through an oilfilter is an ideal location for a particle-attracting magnet. Magnetswith alternating opposing poles (N for north and S for south) are mosteffective in particle removal.
When is the right time to changeoil and filters? Engine builders’ public recommended intervals oftenuse charts that factor in conditions, as well as mileage or hours. Youwill never go wrong if you adhere to these recommendations, or if youchange oil even more often.
One newer engine model has anadvertised oil change interval of 50,000 to 65,000 miles betweenchanges, and that includes the standard primary-secondary filter andsynthetic heavy duty diesel motor oil. Will this be the standardsomeday? Who knows, but for now, stick with the basics.
Currently,about 400 million oil filters are manufactured in the U.S. each year.About another 20 million are imported, resulting in total annual oilfilter sales of about 420 million. Roughly 45% of passenger car oilfilters are sold to do-it-yourselfers.
