Originally Posted By: jacobs
Originally Posted By: Linctex
Originally Posted By: Bluestream
Remember filters become more efficient with use
Yeah, but nobody really wants to hear that.
About 50 years ago, Southwest Research Institute took a Mack diesel engine and installed radioactive piston rings in it. That way they could monitor piston ring wear by the amount of radiation in the engine oil. After establishing a baseline, they gradually fed fine dust into the inlet of a dry paper element. There was a spike in the wear until a “cake” of dust had developed on the filter element then the wear quickly dropped to almost nothing as in their previous baseline. They also installed an oil bath air filter but as I recall quickly discontinued that test due to excessive wear. This test was published by the Society of Automotive Engineers (SAE) but I haven't been able to find it on their website.
Since reading that paper years ago, I seldom replace air filter elements but wait until the rubber seals start to get hard. I do clean them by gently tapping the dirt out of them. I have over 350,000 miles on two different vehicles and have not experienced any obvious loss of performance or loss of fuel mileage.
Good stuff-- if filtration element is still filtering and the edge seal is still pliable to form a seal it is good to go.
Before reading the testimonial above, my thought was that without a restriction gauge telling you when to [clean or replace], miles should be used as a general guide and adjusted for conditions.
Mine went 40k before I opened them up, 30k with a lot of dusty driving.